Stockholders' Equity (Details) (USD $)	3 Months Ended			20 Months Ended	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 2012 Repurchase Program [Member]	Mar. 31, 2014 2012 Repurchase Program [Member]	Mar. 31, 2014 Performance Shares [Member]	Mar. 31, 2013 Performance Shares [Member]
Class of Stock [Line Items]
Allocated Share-based Compensation Expense	$ 2,729,000	$ 2,926,000			$ 500,000	$ 400,000
Stock Repurchase Program, Authorized Amount			50,000,000
Payments for Repurchase of Common Stock	4,069,000	0	4,064,000	25,000,000
Treasury Stock, Shares, Acquired			145,737	1,030,382
Treasury Stock Acquired, Average Cost Per Share			$ 27.92	$ 24.29
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 25,000,000