Shareholder's equity (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	12 Months Ended
	Feb. 20, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 04, 2019	Jul. 17, 2019	Jul. 11, 2018
Stock repurchases
Repurchase of common stock (in shares)		41,020,000	16,844,000	12,967,000
Value of treasury stock acquired		$ 2,402,475	$ 1,153,511	$ 810,949
Treasury stock acquired, average cost per share		$ 58.57	$ 68.48	$ 62.54
Stock Repurchase Program, Additional Authorized Amount							$ 1,389,999
Stock Repurchase Program, Remaining Authorized Repurchase Amount							$ 110,001
Stock Repurchase Program, Authorized Amount					$ 2,000,000	$ 2,000,000
Terminated Remaining Prior Share Repurchases Authorized, Amount					$ 246,373	$ 1,005,605
Charter documents and Delaware law:
Preferred stock, shares authorized (in shares)		5,000,000	5,000,000
Period During Which The Company Is Subject To Section 203 Of The Delaware General Corporation Law Limitation		3 years
Payments to Noncontrolling Interests		$ 68,019	$ 28,082	$ 5,357
Subsequent Event
Stock repurchases
Repurchase of common stock (in shares)	291,000
Value of treasury stock acquired	$ 21,794
Treasury stock acquired, average cost per share	$ 74.92
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 1,681,701