Estimated Subsidies Under Medicare Prescription Drug Improvement and Modernization Act (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
2013	$ 8
2014	8
2015	8
2016	8
2017	8
2018-2022	$ 38

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Amount of the prescription drug subsidy receipts to be received after the fifth fiscal year following the latest fiscal year.

+ 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=28361610&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

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Amount of the prescription drug subsidy receipts to be received in the next fiscal year following the latest fiscal year.

+ References

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Amount of the prescription drug subsidy receipts to be received in the fifth fiscal year following the latest fiscal year.

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Amount of the prescription drug subsidy receipts to be received in the fourth fiscal year following the latest fiscal year.

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Amount of the prescription drug subsidy receipts to be received in the third fiscal year following the latest fiscal year.

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Amount of the prescription drug subsidy receipts to be received in the second fiscal year following the latest fiscal year.

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