Stock-based Compensation (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Taxes paid related to net share settlement of restricted stock units			$ (11,208,000)	$ (485,000)
Unamortized stock based compensation expense	9,400,000		9,400,000
Total stock-based compensation expense			3,750,000	2,518,000
Stock-based Compensation (Textual) [Abstract]
Shares of common stock authorized for issuance	1,800,000		1,800,000
Shares of common stock available for issuance			556,542
Restricted stock units maximum term in years			3 years
Vesting period of stock options in years			3 years
Contractual life of stock options in years			10 years
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs Paid to settle tax withholding obligations			139,790
Taxes paid related to net share settlement of restricted stock units			(11,208,000)
Weighted average remaining amortization period in years			1 year 8 months 12 days
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock granted
Recognized stock-based compensation expense	2,100,000	1,700,000	3,700,000	2,500,000
Unamortized stock based compensation expense	$ 300,000		$ 300,000
Weighted average remaining amortization period in years			1 year 1 month 6 days