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Retirement Benefit Obligations - Additional Information (Detail) (USD $) | 9 Months Ended
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Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items] |
Contributions to Pension plan | $ 9,400,000
Other Postretirement Benefit Plans, Defined Benefit |
Defined Benefit Plan Disclosure [Line Items] |
Contributions to Pension plan | 2,200,000
Supplemental Employee Retirement Plans, Defined Benefit |
Defined Benefit Plan Disclosure [Line Items] |
Contributions to Pension plan | 40,000.0
Expected additional contribution to SERP plan | $ 13,000

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