Income Taxes (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Income Taxes (Textual) [Abstract]
Reduction in taxes payable as a result of the exercise and vesting of equity based compensation	$ 8,990	$ 15,609	$ 6,795
Excess tax benefit associated with equity-based compensation	4,763	11,997	4,054
Increase (reduction) to tax expense	0	1,547	1,142
Additional increase to tax expense		1,580
Recorded reduction to tax expense due to reversal of certain tax contingencies		563	1,269
Significant federal and state net operating loss carryforwards	0	0
Total gross unrecognized tax benefits	0	341	942	1,764
Amount of unrecognized tax benefits (net of the federal benefit on state amounts) that would impact effective tax rate	0	327
Accrual for interest, net of tax		29
Accrual for penalties		0
Expense for interest, net of tax	29	85
Expense for penalties	$ 0	$ 0