Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Information [Line Items]
Total revenue	$ 4,947	$ 4,916	$ 4,626	$ 3,534	$ 3,710	$ 2,581	$ 1,984	$ 1,290	$ 18,023	$ 9,565
Gross profit	(4,766)	694	(2,101)	1,814	405	(2,003)	976	874	(4,359)	252
Income tax benefit					(7,733)	(6,245)	(5,400)	(7,410)		(26,788)	(9)
Net loss	$ (28,034)	$ (39,701)	$ (16,379)	$ (34,198)	$ (30,856)	$ (27,392)	$ (30,249)	$ (13,530)	$ (118,312)	$ (102,027)	$ (73,109)
Net loss per common share: Basic and diluted	$ (0.39)	$ (0.56)	$ (0.23)	$ (0.49)	$ (0.44)	$ (0.39)	$ (0.43)	$ (0.19)	$ (1.67)	$ (1.46)	$ (1.08)
Weighted average shares Basic and diluted	71,119	70,956	70,721	70,470	70,235	70,122	70,075	69,995	70,819	70,117