Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurement - Additional Information (Detail)

v2.4.1.9
Fair Value Measurement - Additional Information (Detail) (Senior Notes, 5.625% Senior Notes, USD $)
Nov. 30, 2014
Aug. 31, 2014
Apr. 16, 2012
Senior Notes | 5.625% Senior Notes
     
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Face amount $ 300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
  $ 300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Debt instrument, interest rate 5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
  5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Fair value of long-term debt $ 313,500,000us-gaap_LongTermDebtFairValue
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
$ 315,800,000us-gaap_LongTermDebtFairValue
/ us-gaap_DebtInstrumentAxis
= atu_FivePointSixTwoFiveSeniorNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember