Earnings Per Share (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	3 Months Ended		64 Months Ended
	May. 09, 2016	Mar. 31, 2016	Mar. 31, 2015	May. 09, 2016
Earnings Per Share
Common stock repurchased, shares		1,231	650
Common stock repurchased, average price per share		$ 254.02	$ 207.50
Common stock repurchased, value		$ 312,637	$ 134,803
Subsequent event [Member]
Earnings Per Share
Common stock repurchased, shares	500			52,900
Common stock repurchased, average price per share	$ 268.74			$ 109.43
Common stock repurchased, value	$ 124,100			$ 5,800,000