Employee Benefit Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Compensation and Retirement Disclosure [Abstract]
Defined contribution plan, maximum annual contribution by employee, percent of eligible earnings	80.00%
Defined contribution plan, employer matching contribution per employee, amount	$ 1,500
Defined contribution plan, employer discretionary contribution amount	$ 1,200,000	$ 1,200,000	$ 902,000
Defined contribution plan, period after which cliff vest occurs	1 year