Share Repurchase Program (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands				2 Months Ended	12 Months Ended		74 Months Ended
	Nov. 16, 2016	May 27, 2016	Feb. 10, 2016	Feb. 28, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2017
Share Repurchase Program
Increase in authorized amount	$ 750,000	$ 750,000	$ 750,000
Cumulative authorized amount	$ 7,800,000
Authorization effective period	3 years	3 years	3 years
Remaining balance under share repurchase program					$ 887,800
Common stock repurchased, shares					5,698	4,901
Common stock repurchased, average price per share					$ 264.21	$ 231.81
Common stock repurchased, value					$ 1,505,371	$ 1,136,139
Subsequent event [Member]
Share Repurchase Program
Common stock repurchased, shares				1,400			58,400
Common stock repurchased, average price per share				$ 267.32			$ 124.14
Common stock repurchased, value				$ 387,500			$ 7,200,000