Principal Balance Unamortized Discount and Net Carrying Amount (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Liability component, principal balance	$ 293,382
Liability component, unamortized discount	70,468
Liability component, net carrying amount	222,914
Senior Notes Due 2019
Debt Instrument [Line Items]
Liability component, principal balance	170,941
Liability component, unamortized discount	45,114
Liability component, net carrying amount	125,827
Senior Convertible Notes Due 2018
Debt Instrument [Line Items]
Liability component, principal balance	122,441
Liability component, unamortized discount	25,354	54,542
Liability component, net carrying amount	$ 97,087

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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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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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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