Information Pertaining to 2022 Notes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		109 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014
Convertible Debt [Line Items]
Balance - December 31, 2013			$ 14,501
Amortization of debt discount			1,199
(Gain) loss from change in fair value of embedded derivative	(1,480)	(2,023)	(2,744)	(693)	(22,858)
Balance - June 30, 2014	12,956		12,956		12,956
Embedded Derivatives
Convertible Debt [Line Items]
Balance - December 31, 2013			3,470
Amortization of debt discount
(Gain) loss from change in fair value of embedded derivative			(2,744)
Balance - June 30, 2014	726		726		726
Principal Amount of Convertible Notes
Convertible Debt [Line Items]
Balance - December 31, 2013			26,900
Amortization of debt discount
(Gain) loss from change in fair value of embedded derivative
Balance - June 30, 2014	26,900		26,900		26,900
Debt Discount
Convertible Debt [Line Items]
Balance - December 31, 2013			(15,869)
Amortization of debt discount			1,199
(Gain) loss from change in fair value of embedded derivative
Balance - June 30, 2014	$ (14,670)		$ (14,670)		$ (14,670)