Repurchases Of Common Stock (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Shares of common stock repurchases authorized	65,000,000
Remaining shares available for repurchase under authorization	3,735,508
Share repurchases during the period	3,071,000	5,659,000	9,761,000
Shares acquired through employee surrenders	60,000	69,000	92,000
Total shares repurchased	3,131,000	5,728,000	9,853,000
Cost of share repurchases during the period | $	$ 313,072	$ 406,430	$ 618,158
Cost of employee surrenders | $	4,372	5,457	5,809
Total cost of shares repurchased | $	$ 317,444	$ 411,887	$ 623,967
Average cost per share | $ / shares	$ 101.40	$ 71.90	$ 63.32
Stock split	2
Treasury Stock [Member]
Total shares repurchased		4,313,000	4,927,000