Share Repurchase Program (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	3 Months Ended		76 Months Ended
	May 08, 2017	Mar. 31, 2017	Mar. 31, 2016	May 08, 2017
Share Repurchase Program
Cumulative authorized amount		$ 7,800,000
Remaining balance under share repurchase program		$ 397,500
Common stock repurchased, shares		1,829	1,231
Common stock repurchased, average price per share		$ 268.09	$ 254.02
Common stock repurchased, value		$ 490,312	$ 312,637
Subsequent event [Member]
Share Repurchase Program
Common stock repurchased, shares	600			59,400
Common stock repurchased, average price per share	$ 254.61			$ 126.40
Common stock repurchased, value	$ 152,200			$ 7,500,000