Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity Shareholders' Equity (Stock Repurchased and Retired) (Details)

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Shareholders' Equity Shareholders' Equity (Stock Repurchased and Retired) (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Shareholders' Equity (Stock Repurchased and Retired) [Abstract]      
Stock Repurchased and Retired During Period, Shares 948 1,011 2,737
Treasury Stock Acquired, Average Cost Per Share $ 61.73 $ 54.87 $ 53.67
Stock Repurchased and Retired During Period, Value $ 58,510 $ 55,467 $ 146,895