Employee Benefit Plans - Share-Based Option Activity - Valuation Assumptions (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Compensation and Retirement Disclosure [Abstract]
Expected volatility	55.80%		65.80%		71.40%
Expected dividend yield	0.00%		0.00%		0.00%
Expected term (in years)	4 years 10 months 24 days		4 years 9 months 18 days		6 years 7 months 6 days
Risk-free interest rate	0.90%		1.10%		2.40%
Weighted average fair value per share of options granted	$ 3.50	[1],[2]	$ 10.55	[1],[2]	$ 15.41	[1]

[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.