Employee Benefit Plans (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Calculated fair value of option award using the Black-Scholes option pricing model
Expected volatility, Minimum	54.63%	54.72%	54.63%	54.72%
Expected volatility, Maximum	54.75%	54.77%	56.14%	56.09%
Risk-free interest rate, Minimum	0.95%	2.18%	0.94%	2.18%
Risk-free interest rate, Maximum	0.98%	2.23%	1.74%	2.72%
Dividend yield
Maximum [Member]
Calculated fair value of option award using the Black-Scholes option pricing model
Fair value of underlying stock per share	10.66	12.1	9.59	10.98
Expected term	5 years 11 months 9 days	5 years 10 months 24 days	5 years 3 months 7 days	5 years 5 months 19 days
Minimum [Member]
Calculated fair value of option award using the Black-Scholes option pricing model
Fair value of underlying stock per share			10.66	12.1
Expected term	6 years 29 days	9 years 26 days	8 years 6 months	6 years 29 days