Share Repurchase Program (Schedule of Shares Repurchased) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Repurchase Program
Shares repurchased	185	1,633	1,669	2,560
Average price per share	$ 417.79	$ 366.76	$ 390.14	$ 359.63
Total investment	$ 76,974	$ 598,846	$ 651,011	$ 920,692

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

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Balance Type:	na
Period Type:	duration