Derivative Financial Instruments - Additional Information (Detail) (USD $)	9 Months Ended
Sep. 30, 2012
Derivative [Line Items]
Estimated net loss reclassified from accumulated comprehensive income into earnings	12 months
Estimated net loss reclassified from accumulated comprehensive income into earnings	$ 1,714,000
Cash and cash Equivalents	30,000,000
Deposit of cash collateral in excess	$ 5,000,000

Estimated period for the anticipated transfer of gain (loss), net, from accumulated other comprehensive income into earnings, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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Balance Type:	na
Period Type:	duration