Borrowings - Schedule of Future Minimum Payments under the Loans Payable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Loans payable, net of current portion	$ 105,135	$ 103,427
4.50% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Remainder of 2014	2,813
2015	5,625
2016	5,625
2017	5,625
2018 and thereafter	141,875
Loans payable, gross	161,563
Less interest	(36,563)
Less unamortized discount	(48,413)
Loans payable, net of current portion	76,587
Loans Payable [Member] | Loan and Security Agreement [Member]
Debt Instrument [Line Items]
Remainder of 2014	5,626
2015	18,135
2016	23,804
Loans payable, gross	47,565
Less interest	(6,365)
Less unamortized discount	(1,862)
Less current portion	(10,790)
Loans payable, net of current portion	$ 28,548