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Debt - Additional Information (Details) (USD $)
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3 Months Ended |
0 Months Ended |
3 Months Ended |
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Feb. 28, 2015
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Apr. 16, 2012
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Dec. 31, 2015
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| Debt Instrument [Line Items] |
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| Senior credit facility expansion option, available |
350,000,000atu_LineOfCreditFacilityAdditionalExpansionOptionAvailable
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| Debt Instrument, actual interest rate |
1.94%us-gaap_DebtInstrumentInterestRateEffectivePercentage
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| Libor Rate |
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| Debt Instrument [Line Items] |
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| Debt instrument, interest rate over variable rate |
1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
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| Revolving Credit Facility |
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| Debt Instrument [Line Items] |
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| Maximum borrowing capacity |
600,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Senior Credit Facility - Term Loan |
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| Debt Instrument [Line Items] |
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| Maximum borrowing capacity |
90,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= atu_SeniorCreditFacilityTermLoanMember
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| Quarterly installments, payable on term loan |
1,100,000us-gaap_LineOfCreditFacilityPeriodicPayment
/ us-gaap_CreditFacilityAxis
= atu_SeniorCreditFacilityTermLoanMember
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| Line of Credit | Senior Credit Facility - Revolver |
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| Debt Instrument [Line Items] |
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| Unused credit line |
389,300,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ us-gaap_DebtInstrumentAxis
= atu_SeniorCreditFacilityRevolverMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
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| Unused credit line Available for Borrowing, Amount |
328,000,000atu_DebtInstrumentUnusedBorrowingCapacityAvailableforBorrowingAmount
/ us-gaap_DebtInstrumentAxis
= atu_SeniorCreditFacilityRevolverMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
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| Senior Notes | 5.625% Senior Notes |
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| Debt Instrument [Line Items] |
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| Debt Instrument, actual interest rate |
104.50%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Debt Instrument, Face Amount |
300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Debt instrument, interest rate |
5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Debt Instrument, Repurchase Amount |
150,000,000us-gaap_DebtInstrumentRepurchaseAmount
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Minimum |
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| Debt Instrument [Line Items] |
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| Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |
0.15%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
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| Interest coverage ratio |
3.50atu_Interestcoverageratio
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
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| Minimum | Libor Rate |
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| Debt Instrument [Line Items] |
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| Debt instrument, interest rate over variable rate |
1.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
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| Minimum | Base Rate |
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| Debt Instrument [Line Items] |
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| Debt instrument, interest rate over variable rate |
0.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember
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| Minimum | Senior Notes | 5.625% Senior Notes |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Redemption Price, Percentage |
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100.00%us-gaap_DebtInstrumentRedemptionPricePercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
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| Maximum |
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| Debt Instrument [Line Items] |
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| Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |
0.40%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
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| Leverage ratio |
3.75atu_LeverageRatio
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
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| Maximum | Libor Rate |
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| Debt Instrument [Line Items] |
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| Debt instrument, interest rate over variable rate |
2.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
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| Maximum | Base Rate |
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| Debt Instrument [Line Items] |
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| Debt instrument, interest rate over variable rate |
1.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember
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| Maximum | Senior Notes | 5.625% Senior Notes |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Redemption Price, Percentage |
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102.80%us-gaap_DebtInstrumentRedemptionPricePercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
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| Scenario, Forecast | Senior Credit Facility - Term Loan |
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| Debt Instrument [Line Items] |
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| Quarterly installments, payable on term loan |
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$ 2,300,000us-gaap_LineOfCreditFacilityPeriodicPayment
/ us-gaap_CreditFacilityAxis
= atu_SeniorCreditFacilityTermLoanMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
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