Benefit Obligations - Benefit Payments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Year ending December 31, 2013	$ 91,515
Year ending December 31, 2014	89,133
Year ending December 31, 2015	89,148
Year ending December 31, 2016	90,620
Year ending December 31, 2017	89,015
Years ending December 31, 2018 through December 31, 2022	447,377
Post-retirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Year ending December 31, 2013	850
Year ending December 31, 2014	930
Year ending December 31, 2015	1,020
Year ending December 31, 2016	1,120
Year ending December 31, 2017	1,240
Years ending December 31, 2018 through December 31, 2022	$ 8,820

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Amount of benefits expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year from a defined benefit 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 (f)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

+ Details

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- Definition

Amount of benefits expected to be paid in the next fiscal year following the latest fiscal year from a defined benefit plan.

+ References

+ Details

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- Definition

Amount of benefits expected to be paid in the fifth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

+ Details

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- Definition

Amount of benefits expected to be paid in the fourth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

+ Details

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- Definition

Amount of benefits expected to be paid in the third fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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- Definition

Amount of benefits expected to be paid in the second fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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