Stockholders' Equity (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payments for Repurchase of Common Stock	$ 93,218,000	$ 63,585,000	$ 850,000
Remaining Number of Shares Authorized to be Repurchased	3,000,000
Shares Paid for Tax Withholding for Share Based Compensation	82,000	14,000	22,000
Payments related to tax withholding for share based compensation (in USD)	2,600,000	500,000	900,000
Repurchase plan authorized in Oct 2008 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased (in shares)	6,000,000
Stock Repurchased and Retired During Period, Shares	2,800,000	2,000,000	0
Payments for Repurchase of Common Stock	$ 90,600,000	$ 63,100,000
Repurchase plan authorized in Oct 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased (in shares)	3,000,000.0