Stockholders Equity - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended			1 Months Ended
	Mar. 31, 2013	May 31, 2012	Feb. 28, 2011	Feb. 28, 2011 4.75% Convertible Notes Due Two Thousand Eighteen	May 31, 2012 Senior Convertible Notes Due 2018	May 09, 2012 Senior Convertible Notes Due 2018
Schedule of Capitalization, Equity [Line Items]
Convertible notes exchanged, warrants issued to purchase common stock					4.0
Convertible notes exchanged, warrants exercise price						1.863
Warrant liability, fair value	$ 2,200,000	$ 5,300,000
Realized gain on change in valuation of warrant liability	745,000
Principal amount of issued debt	1,000			230,000,000
Convertible senior notes, maturity date	May 09, 2019			Feb. 01, 2018
Conversion feature of Convertible Notes				35,600,000
Deferred tax liability set-up related to the Convertible Notes (net of finance costs)			22,700,000
Issuance costs				$ 1,900,000