Employee Benefit Plan (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Jan. 31, 2008	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jan. 31, 2012 Employee Benefit Plan [Member]	Dec. 31, 2012 Employee Benefit Plan [Member]
Employee Benefit Plan [Abstract]
Employee benefit plan		$ 3,400,000	$ 2,600,000	$ 1,900,000
Percentage of company match that vests annually		25.00%
Subsequent Event [Line Items]
Employee benefit plan, amended matching contribution	1/2				1/2
Percentage of employee contribution matched by the company	8.00%				8.00%
Maximum amount that company will match annually per employee (whole number)		$ 2,000	$ 2,000	$ 2,000		$ 4,000