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Derivative Financial Instruments - Impact of Derivatives on Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Offsetting [Abstract]
Amount of after-tax net losses to be reclassified from accumulated other comprehensive income to earnings in the next 12 months	$ 0.3

X

- Definition

Expected after reclassification from accumulated other comprehensive income earnings related amortization of basis of designated cash flow hedge and closed futures contracts.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_OffsettingAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration