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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Fair Value of Financial Instruments - Additional Information (Detail) (USD $)			1 Months Ended	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2012 Certificates of deposit Maximum	Mar. 31, 2012 Certificates of deposit Maximum	Mar. 31, 2013 Senior Notes Due 2019	Mar. 31, 2013 Senior Convertible Notes Due 2018	Mar. 31, 2013 Senior Convertible Notes Due 2018 Level 3
Fair Value of Financial Instruments [Line Items]
Short-term investment in certificates of deposits, maturity term			1 year	1 year
Notes, outstanding	$ 293,382,000	$ 293,382,000			$ 170,900,000	$ 122,400,000
Notes, carrying value	128,986,000	125,827,000			129,000,000
Notes, fair value					118,200,000		36,100,000
Notes, carrying value	$ 98,058,000	$ 97,087,000				$ 98,100,000