Carrying Amount of Components of Convertible Notes (Detail) (4.50% Convertible Notes due 2012, USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
4.50% Convertible Notes due 2012
Debt Outstanding [Line Items]
Principal	$ 4,915	$ 230,000
Unamortized discount	(169)	(15,951)
Net carrying amount of liability component	4,746	214,049
Carrying amount of equity component	$ 35,201	$ 36,850

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant