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Employee Benefits And Stock-Based Compensation Employee Benefits And Stock-Based Compensation (Share-based Compensation by award type) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation $ 52,907 $ 50,044 $ 46,075
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount (2,455) (2,386) (2,718)
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation 38,087 37,325 36,664
Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation 13,270 11,512 8,078
Employee Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation $ 4,005 $ 3,593 $ 4,051