Components of Retirement Plan Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Plans
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Service Cost	$ 753	$ 893	$ 2,255	$ 2,680
Interest Cost	1,273	1,142	3,819	3,425
Expected Return on Plan Assets	(1,562)	(1,488)	(4,684)	(4,466)
Prior Service Cost Amortization	52	52	158	156
Actuarial Loss Amortization	711	1,057	2,135	3,172
Sub-total	1,227	1,656	3,683	4,967
Amounts Capitalized and Deferred	(556)	(805)	(1,400)	(2,189)
Net Periodic Benefit Cost Recognized	671	851	2,283	2,778
Other Postretirement Benefit Plans, Defined Benefit
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Service Cost	497	630	1,491	1,892
Interest Cost	671	612	2,015	1,836
Expected Return on Plan Assets	(230)	(180)	(690)	(541)
Prior Service Cost Amortization	421	425	1,261	1,275
Actuarial Loss Amortization	14	197	42	590
Sub-total	1,373	1,684	4,119	5,052
Amounts Capitalized and Deferred	(632)	(808)	(1,697)	(2,255)
Net Periodic Benefit Cost Recognized	741	876	2,422	2,797
Supplemental Employee Retirement Plans, Defined Benefit
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Service Cost	15	19	43	55
Interest Cost	68	60	204	181
Prior Service Cost Amortization	2	2	8	8
Actuarial Loss Amortization	25	46	75	138
Sub-total	110	127	330	382
Net Periodic Benefit Cost Recognized	$ 110	$ 127	$ 330	$ 382

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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- 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

-URI http://asc.fasb.org/extlink&oid=6512171

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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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.

+ References

+ Details

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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.

+ References

+ Details

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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

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

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

-URI http://asc.fasb.org/extlink&oid=6525008

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

Amounts of pension and other post retirement benefit costs capitalized and deferred.

+ References

No definition available.

+ Details

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- Definition

The gross 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 or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments).

+ References

No definition available.

+ Details

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