Share Repurchase Program (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands			2 Months Ended	12 Months Ended		98 Months Ended
	Nov. 13, 2018	Feb. 07, 2018	Feb. 27, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 27, 2019
Share Repurchase Program
Increase in authorized amount	$ 1,000,000	$ 1,000,000
Cumulative authorized amount	$ 11,800,000
Authorization effective period	3 years	3 years
Remaining balance under share repurchase program				$ 1,000,000
Common stock repurchased, shares				6,061	9,301
Common stock repurchased, average price per share				$ 282.80	$ 233.57
Common stock repurchased, value				$ 1,713,953	$ 2,172,437
Subsequent event [Member]
Share Repurchase Program
Common stock repurchased, shares			800			73,100
Common stock repurchased, average price per share			$ 342.95			$ 150.73
Common stock repurchased, value			$ 268,900			$ 11,000,000