Stock-Based Compensation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Number of options granted	54,500	157,500	500,000
Exercise price	$ 17.57	$ 13.18	$ 7.52
Vesting term	4 years 6 months	5 years	5 years
Contractual term	5 years 6 months	6 years	6 years
Grant-date fair value	$ 6.80	$ 4.63	$ 3.15
Black-Scholes assumptions:
Expected term	4 years 2 months 12 days	4 years 6 months	4 years 7 months 6 days
Expected stock price volatility	48.30%	39.30%	47.60%
Risk-free interest rate	0.61%	1.82%	2.15%
Expected dividend yield	0.00%	0.00%	0.00%