Debt - Schedule of Total Interest Expense on Convertible Senior Notes (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 565,000	$ 583,000
Accretion of debt discount (Non-cash)			1,822,000	1,110,000
Senior Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense (Cash)	2,139,000	2,138,000	4,277,000	2,518,000
Amortization of debt issuance costs	228,000	215,000	452,000	249,000
Accretion of debt discount (Non-cash)	890,000	841,000	1,764,000	973,000
Total interest expense	3,257,000	3,194,000	6,493,000	3,740,000
Effective interest rate of the liability component	7.32%	7.36%	7.32%	7.32%
Fair Value, Inputs, Level 1 | Senior Convertible Notes
Debt Instrument [Line Items]
Fair Value of principal amount of notes	$ 221,900,000		$ 221,900,000