Treasury Stock Purchases (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended	10 Months Ended	12 Months Ended
	Mar. 31, 2010	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Mar. 05, 2010	Dec. 31, 2009
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 30,000,000
Treasury Stock, Shares, Acquired		0.3
Treasury Stock, Value, Acquired, Cost Method	0	2,900,000	5,745,000	4,948,000		6,543,000
Shares Paid for Tax Withholding for Share Based Compensation			0.2	0.2
Adjustments Related to Tax Withholding for Share-based Compensation			5,700,000	4,900,000
Treasury Stock Acquired through Purchase Agreement, Private Equity Firm						0.1
Treasury Stock Acquired through Purchase Agreement, Private Equity Firm, Value						$ 2,000,000
Treasury Stock Acquired through Purchase Agreement, Private Equity Firm, Price per Share						$ 20
Minimum [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury Stock Acquired, Cost Per Share		$ 10.34
Shares Repurchased for Tax Withholding for Share Based Compensation, Price Range			$ 23.11	$ 21.34
Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury Stock Acquired, Cost Per Share		$ 11.00
Shares Repurchased for Tax Withholding for Share Based Compensation, Price Range			$ 33.53	$ 30.06