Segment information - Revenues Generated in United States and All International Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 595,696	$ 559,508	$ 1,551,701	$ 1,430,102
United States
Segment Reporting Information [Line Items]
Revenues	559,057	522,159	1,463,129	1,340,254
International
Segment Reporting Information [Line Items]
Revenues	$ 36,639	$ 37,349	$ 88,572	$ 89,848