Schedule of Components of Net Periodic Benefit Cost (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]
Service cost	$ 17,125	$ 16,121	$ 13,084
Interest cost	28,935	23,016	23,653
Expected return on assets	(32,661)	(26,660)	(23,899)
Prior service cost	445	449	466
Actuarial (gain) loss	4,045	15,679	12,417
Transition asset	(1)	(1)	(1)
Settlement charge		729	779
Termination benefit charge	13,652
Net periodic benefit cost	31,540	29,333	26,499
Postretirement Benefits
Pension and Other Postretirement Benefits Disclosure [Line Items]
Service cost	206	227	227
Interest cost	1,164	1,013	1,234
Prior service cost	(3,255)	(3,255)	(3,255)
Actuarial (gain) loss	(266)	25	(283)
Net periodic benefit cost	$ (2,151)	$ (1,990)	$ (2,077)

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.

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

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- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Return on Plan Assets

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-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

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-SubTopic 20

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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- Definition

The amount of net gain (loss) recognized in net periodic benefit cost as a result of an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

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-Subparagraph (h)(7)

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-Glossary Plan Curtailment

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-Topic 715

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-Paragraph 6

-Subparagraph (a)(2)

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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.

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- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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-Publisher FASB

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-Glossary Service Cost (Component of Net Periodic Pension Cost)

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