Share repurchases Share Repurchase Table (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
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock (in shares)	8,232	30,592	12,284	32,652
Value of treasury stock acquired	$ 725,439	$ 1,747,968	$ 1,028,578	$ 1,860,157
Treasury stock acquired, average cost per share	$ 88.13	$ 57.14	$ 83.73	$ 56.97
Open Market Purchases
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock (in shares)	250	8,790	4,302	10,850
Value of treasury stock acquired	$ 21,259	$ 514,082	$ 324,398	$ 626,271
Treasury stock acquired, average cost per share	$ 85.04	$ 58.49	$ 75.40	$ 57.72
Tender Offer
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock (in shares)	7,982	21,802	7,982	21,802
Value of treasury stock acquired	$ 704,180	$ 1,233,886	$ 704,180	$ 1,233,886
Treasury stock acquired, average cost per share	$ 88.22	$ 56.60	$ 88.22	$ 56.60
Treasury Stock, Share Repurchases, Table Footnotes [Abstract]
Treasury Stock Acquired Average Cost Per Share Clearing Price	$ 88.00	$ 56.50	$ 88.00	$ 56.50
Share Repurchase Fees And Expenses	$ 1,792	$ 2,074	$ 1,792	$ 2,074