Net Periodic benefit Cost Recognized in Comprehensive Earnings (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension
Pension and Other Postretirement Benefits Disclosure [Line Items]
Actuarial loss (gain)	$ 105,546	$ (90,755)	$ 47,877
Prior service cost	(445)	(449)	(466)
Actuarial gain (loss)	(4,045)	(15,679)	(12,417)
Transition asset	1	1	1
Settlement charge		(729)	(779)
Total	101,057	(107,611)	34,216
Postretirement Benefits
Pension and Other Postretirement Benefits Disclosure [Line Items]
Actuarial loss (gain)	(3,026)	(1,011)	1,993
Prior service cost	3,255	3,255	3,255
Actuarial gain (loss)	266	(25)	283
Total	$ 495	$ 2,219	$ 5,531

The amount of gains or losses recognized in net periodic benefit cost.

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- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ References

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The amount of the transition obligation or asset recognized in net periodic benefit cost.

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- Definition

Amount before tax, after reclassification adjustments, of actuarial gain (loss) that has not been recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

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- Definition

Amount of net gain (loss) recognized in net periodic benefit cost as a result of an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include, but are not limited to, lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contracts to cover vested benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Topic 715

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Amount before tax of (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

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