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Pension and Other Postretirement Benefit Plans - Summary of Net Period Benefit Costs (Detail) (USD $)
In Thousands, unless otherwise specified |
3 Months Ended | |
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Mar. 31, 2014
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Mar. 31, 2013
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Pension Benefits [Member]
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| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | ||
| Interest cost | $ 4,900 | $ 4,500 |
| Expected return on plan assets | (6,025) | (5,950) |
| Amortization of prior service credit | (358) | (358) |
| Amortization of actuarial gain | 1,200 | 1,840 |
| Net periodic (credit) cost | (283) | 32 |
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Other Benefits [Member]
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| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | ||
| Interest cost | 2 | 10 |
| Amortization of prior service credit | (3,087) | |
| Amortization of actuarial gain | (33) | (481) |
| Net periodic (credit) cost | $ (31) | $ (3,558) |