Summary of Significant Accounting Policies (Earnings Per Share) (Weighted Average Common Shares Outstanding) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Basic And Diluted Weighted Average Common Shares Outstanding [Line Items]
Basic weighted-average common shares outstanding	114,432	112,037	110,617
Diluted weighted-average common shares outstanding	118,439	117,586	115,865
Employee stock option
Schedule of Basic And Diluted Weighted Average Common Shares Outstanding [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	3,755	5,340	4,924
Restricted stock awards
Schedule of Basic And Diluted Weighted Average Common Shares Outstanding [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	170	209	324
Performance-based restricted stock awards
Schedule of Basic And Diluted Weighted Average Common Shares Outstanding [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	82	0	0