Fair Value of Financial Instruments and Investments - Additional Information (Detail) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Fair Value of Financial Instruments [Line Items]
Notes, outstanding	$ 293,382,000
Notes, carrying value	95,216,000	175,458,000
Notes, carrying value	119,838,000
Senior Convertible Notes Due 2018
Fair Value of Financial Instruments [Line Items]
Notes, outstanding	122,400,000	230,000,000
Notes, carrying value	95,216,000	175,458,000
Senior Notes Due Two Thousand Nineteen
Fair Value of Financial Instruments [Line Items]
Notes, outstanding	170,900,000
Notes, fair value	118,200,000
Notes, carrying value	119,838,000
Level 3 \| Senior Convertible Notes Due 2018
Fair Value of Financial Instruments [Line Items]
Notes, fair value	$ 30,300,000	$ 116,400,000

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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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents notes payable as of the balance sheet date.

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