Long-term Debt (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
6.375% notes, due 2012, net of unamortized discount of $38
Debt Instrument [Line Items]
Notes payable, unamortized discount	$ 38
7.05% notes, due 2029, net of unamortized discount of $1,616
Debt Instrument [Line Items]
Notes payable, unamortized discount	$ 1,616

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant