Employee Benefit Plans - Summary of Share-Based Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Compensation and Retirement Disclosure [Abstract]
Shares Outstanding	8,478,148	[1]	8,744,649	[1]	7,390,191	[1]
Shares Granted	8,173,944	[1]	2,252,457	[1]
Shares Exercised	0		0
Shares Canceled	(8,440,445)	[1]	(897,999)	[1]
Shares Outstanding	8,744,649	[1]	7,390,191	[1]
Shares Vested and expected to vest at December 31, 2012	6,283,159	[1]
Shares Exercisable at December 31	1,395,374	[1]	1,780,770	[1]
Weighted Average Exercise Price Outstanding	$ 10.51	[1]	$ 38.15	[1]	$ 46.35	[1]
Weighted Average Exercise Price Granted	$ 8.44	[1]	$ 26.23	[1]
Weighted Average Exercise Price Exercised	$ 0.00		$ 0
Weighted Average Exercise Price Canceled	$ 31.08	[1]	$ 42.67	[1]
Weighted Average Exercise Price Outstanding	$ 38.15	[1]	$ 46.35	[1]
Weighted Average Exercise Price Vested and expected to vest at December 31, 2012	$ 10.54	[1]
Weighted Average Exercise Price Exercisable at December 31	$ 10.65	[1]	$ 43.69	[1]
Weighted Average Grant Date Fair Value Outstanding	$ 16.48	[1],[2]	$ 18.06	[1],[2]
Weighted Average Grant Date Fair Value Outstanding Granted	$ 3.50	[1],[2]	$ 10.55	[1],[2]	$ 15.41	[1]
Weighted Average Grant Date Fair Value Outstanding Exercised	$ 0.00		$ 0
Weighted Average Grant Date Fair Value Outstanding Cancelled	$ 16.36	[1],[2]	$ 16.67	[1],[2]
Weighted Average Grant Date Fair Value Outstanding Exercisable	$ 3.80	[1],[2]	$ 19.53	[1],[2]
Weighted Average Grant Date Fair Value Outstanding Vested and Expected to Vest at December 31, 2012	$ 3.57	[1],[2]
Weighted Average Grant Date Fair Value Outstanding	$ 3.51	[1],[2]	$ 16.48	[1],[2]	$ 18.06	[1],[2]
Weighted Average Remaining Contractual Term Outstanding	9 years 4 months 24 days		7 years 3 months 18 days
Weighted Average Remaining Contractual Term Exercisable	9 years		5 years 4 months 24 days
Weighted Average Remaining Contractual Term Vested and Expected to Vest at December 31, 2012	9 years 4 months 24 days
Weighted Average Remaining Contractual Term Outstanding	9 years 4 months 24 days		7 years 3 months 18 days

[1] Adjusted for the February 2012 1.742-for-one stock split.

[2] Represents the weighted-average grant date fair value per option, using the Monte Carlo simulation option-pricing model for performance-based options, and the Black-Scholes option-pricing model for time-based options.