Employee Benefit Plans - 401(k) Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Benefit and Other Plans [Abstract]
Percent of maximum contribution of pretax income per employee	100.00%
Amount of maximum contribution per employee	$ 17,000
Amount of maximum catch-up contribution	5,500
Vesting period	5
Percentage of discretionary match	25.00%
Maximum percentage of eligible contribution	5.00%
Amount of matching contributions	$ 1,500,000	$ 1,500,000	$ 1,400,000