Stockholders' Equity and Warrants - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended		12 Months Ended
	Jan. 29, 2013	Dec. 20, 2011	Feb. 25, 2009	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 01, 2013	Jun. 20, 2013
Stockholders Equity Note [Line Items]
Preferred stock, authorized				10,000,000	10,000,000
Common stock, authorized				450,000,000	240,000,000				240,000,000
Common stock purchase price	$ 19.60	$ 10.42	$ 1.69
Net proceed from sale of common stock	$ 310,000,000	$ 243,100,000	$ 22,800,000	$ 310,037,000		$ 243,058,000
Warrants issued			10,784,024
Exercise price of warrants			2.15					20.00
Warrants exercised					5,805,843	3,757,767	1,220,414
Proceeds from warrants exercised					12,483,000	8,080,000	2,600,000
Adjustment of additional paid-up capital up on exercise of warrants					$ 87,000,000
Number of preferred share rights issued per share of common stock outstanding								1
Percentage of ownership that triggers rights separation from common stock								4.99%
Percentage of additional shares over 4.99% threshold that would trigger dilutive ownership events if acquired								0.50%
Common stock
Stockholders Equity Note [Line Items]
Shares of common stock sold	16,489,893	24,725,000	14,378,698
Series A Junior Preferred Stock
Stockholders Equity Note [Line Items]
Preferred stock, authorized				500,000
Preferred stock, voting rights				1,000 to 1 basis with each share of common stock.
Number of preferred share rights issued per share of common stock outstanding								0.001