Information Pertaining to 2022 Notes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Debt Instrument [Line Items]
Beginning balance			$ 14,501	$ 25,554
Amortization of debt discount			1,889	2,780
Write-off of debt discount associated with conversion of debt				11,277
Gain from change in fair value of embedded derivative of 2022 note	(726)	(1,587)	(3,470)	(2,280)
Conversion				(22,516)
Ending balance	12,920	14,815	12,920	14,815
Embedded Derivative Financial Instruments
Debt Instrument [Line Items]
Beginning balance			3,470	11,000
Amortization of debt discount			0	0
Write-off of debt discount associated with conversion of debt				0
Gain from change in fair value of embedded derivative of 2022 note			(3,470)	(2,280)
Conversion				(4,416)
Ending balance	0	4,304	0	4,304
Principal Amount of Convertible Notes
Debt Instrument [Line Items]
Beginning balance			26,900	45,000
Amortization of debt discount			0	0
Write-off of debt discount associated with conversion of debt				0
Gain from change in fair value of embedded derivative of 2022 note			0	0
Conversion				(18,100)
Ending balance	26,900	26,900	26,900	26,900
Debt Discount
Debt Instrument [Line Items]
Beginning balance			(15,869)	(30,446)
Amortization of debt discount			1,889	2,780
Write-off of debt discount associated with conversion of debt				11,277
Gain from change in fair value of embedded derivative of 2022 note			0	0
Conversion				0
Ending balance	$ (13,980)	$ (16,389)	$ (13,980)	$ (16,389)