Equity and Liability Components of Notes (Detail) (Convertible Senior Notes, USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2012
Convertible Senior Notes
Debt Instrument [Line Items]
Remaining amortization period of discount on the liability component	5 years 9 months 18 days
Contractual coupon interest expense	$ 956
Accretion of discount on the liability component	650
Principal amount of convertible notes outstanding	150,000
Unamortized discount of liability component	(24,843)
Net carrying amount of liability component	125,157
Less: current portion
Long-term debt	125,157
Carrying value of equity component, net of issuance costs	$ 20,993

Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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Carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Convertible Notes Payable, excluding current portion. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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Interest expense related to convertible debt instruments which has been recognized for the period, including the contractual interest coupon and amortization of the debt discount, if any.

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Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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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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