Senior Secured Notes and Convertible Subordinated Notes - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Jul. 31, 2012	Dec. 31, 2012	Jul. 11, 2012
Line of Credit Facility [Line Items]
Amount reserved			$ 25,000,000
Percentage of repurchase of notes on principal amount of notes		101.00%
Percentage of repurchase of notes on principal amount of notes		100.00%
Convertible subordinated notes remaining			172,400,000
Issuance of Debt [Member]
Line of Credit Facility [Line Items]
Senior secured notes, issued			125,000,000
Maturity date of senior secured notes	Jul. 15, 2017
Retirement of convertible subordinated notes	42,500,000
Interest rate			12.00%
Issuance costs	$ 4,500,000
Maturity date of convertible subordinated notes		Sep. 28, 2012