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Retirement Plans - Defined Benefit Plans - Additional Information (Detail) (USD $)
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12 Months Ended |
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Defined Benefit Plan Disclosure [Line Items] |
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| Curtailment loss |
$ 982,000 |
$ 0 |
$ 1,517,000 |
| Component of curtailment loss comprised of amortization of prior service cost |
500,000 |
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600,000 |
| Component of curtailment loss comprised of net actuarial loss |
465,000 |
0 |
900,000 |
| Amortization of net actuarial loss into net periodic pension cost in next year from accumulated other comprehensive income |
2,000,000 |
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| Amortization of prior service cost into net periodic pension cost in next year from accumulated other comprehensive income |
400,000 |
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| Contribution made by employer |
7,965,000 |
389,000 |
10,700,000 |
| Expected cash contributions in 2015 |
5,200,000 |
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| Accumulated benefit obligation |
103,200,000 |
78,700,000 |
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| Actuarial gain (loss) |
$ 4,000,000 |
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