Share repurchases (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended		3 Months Ended	6 Months Ended
	Aug. 16, 2019	Jul. 17, 2019	Jun. 30, 2019	Jun. 30, 2019
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock (in shares)			2,060	2,060
Value of treasury stock acquired			$ 112,189	$ 112,189
Average cost of treasury stock (usd per share)			$ 54.46	$ 54.46
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock (in shares)		4,214
Value of treasury stock acquired		$ 237,811
Average cost of treasury stock (usd per share)		$ 56.43
Prior shares under repurchase authorization (in shares)		2,000,000
Minimum | Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Tender Offer Treasury Stock Value To Be Acquired	$ 1,200,000
Tender Offer Treasury Stock Price Per Share	$ 53.50
Maximum | Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Tender Offer Treasury Stock Price Per Share	$ 61.50
Forecast | Minimum
Equity, Class of Treasury Stock [Line Items]
Credit Agreement, Lender Commitment	$ 5,250,000