Stock-based Compensation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Summary of stock-based compensation expense recognized by the company
Total recognized stock-based compensation expense	$ 3,781	$ 1,901	$ 6,972	$ 3,003
Stock options [Member]
Summary of stock-based compensation expense recognized by the company
Total recognized stock-based compensation expense	1,673	433	3,062	934
Restricted stock awards [Member]
Summary of stock-based compensation expense recognized by the company
Total recognized stock-based compensation expense		19		42
Restricted stock units [Member]
Summary of stock-based compensation expense recognized by the company
Total recognized stock-based compensation expense	$ 2,108	$ 1,449	$ 3,910	$ 2,027