Share Repurchase Program (Schedule of Shares Repurchased) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Repurchase Program
Shares repurchased	965	1,025	2,634	3,585
Average price per share	$ 458.70	$ 377.85	$ 415.28	$ 364.84
Total investment	$ 442,962	$ 387,255	$ 1,093,973	$ 1,307,947

Number of shares that have been repurchased and retired during the period.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration