Organization and Nature of Business - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Jul. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jul. 21, 1980
Organization And Nature Of Business [Line Items]
Company name change effective date		Jul. 11, 2012
Losses incurred during the period		$ 431,251	$ 309,964
Cash and cash equivalents		$ 187,661	$ 39,904	$ 33,589	$ 48,275	$ 0
Common stock outstanding, reverse stock split	0.167