Income Taxes (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Current income tax expense		$ 900,000	$ 800,000	$ 500,000
Tax benefits associated with equity-based compensation		1,845,000	3,837,000	5,973,000
Net operating losses carry forward		3,900,000
Net operating losses valuation allowances		700,000
Tax credits carry forward		5,100,000
Tax credits carry forward, valuation allowances		1,800,000
Net operating losses carry forward expiration dates		2020
Tax credits carry forward expiration dates		2020
Effective tax rate		37.20%	37.40%	34.40%
Uncertain tax positions liabilities			100,000
Payment of interest and penalties accrued unrecognized tax positions			19,000
Unrecognized tax positions that, if recognized, would affect the effective tax rate			100,000
Uncertain tax positions settlements	$ 5,700,000