Benefit Plans - Components of Net Periodic Pension Expense for Qualified and Non-Qualified Plans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation And Retirement Disclosure [Abstract]
Service cost		$ 7,104	$ 7,338	$ 6,018
Interest cost		6,645	6,516	6,242
Expected return on plan assets		(12,015)	(8,937)	(6,698)
Amortization of prior service cost		898	873	762
Amortization of net loss		1,970	2,401	1,540
Recognized loss due to curtailment	750	750
Total net periodic pension expense		$ 5,352	$ 8,191	$ 7,864

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Amount before tax, after reclassification adjustments, of prior service cost (credit) that has not been recognized in the income statement.

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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

-URI http://asc.fasb.org/extlink&oid=6512136

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

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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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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(7)

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-Name Accounting Standards Codification

-Glossary Plan Curtailment

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-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 15

-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.

+ References

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

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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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

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

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