Related Party Transaction - Narrative (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended				12 Months Ended
	Dec. 31, 2011	Oct. 31, 2010	Aug. 31, 2009	Feb. 28, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Related Party Transaction [Line Items]
Shares of common stock offered for sale	24,725,000	16,000,000	21,850,000	14,378,698
Issuance of common stock	$ 243,058	$ 57,515	$ 35,600	$ 22,800	$ 243,058	$ 57,515	$ 58,370
Chief Executive Officer [Member]
Related Party Transaction [Line Items]
Shares of common stock offered for sale			1,714,286
Offering price of common stock			$ 1.75
Issuance of common stock			$ 3,000