Repurchases Of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Repurchases Of Common Stock [Abstract]
Shares repurchased in the open market	390	708
Shares acquired through employee surrender for statutory tax withholding	52	52
Total shares repurchased	442	760
Cost of shares repurchased in the open market	$ 50,744	$ 49,715
Cost of shares for employee surrenders	7,303	3,529
Total cost of shares	$ 58,047	$ 53,244
Average cost per share - open market repurchase	$ 130.12	$ 70.21
Average cost per share - employee surrenders	141.09	67.96
Average cost per share - total	$ 131.41	$ 70.06