Revenue Recognition - Contract Acquisition Costs (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) In Capitalized Contract Cost [Roll Forward]
Balance at beginning of period	$ 113,592	$ 114,306
Additions	49,366	47,277
Amortization expense	(51,265)	(47,762)
Foreign currency translation	(4,607)	97
Balance at end of period	107,086	113,918
Contract Acquisition Costs
Increase (Decrease) In Capitalized Contract Cost [Roll Forward]
Balance at beginning of period	96,723
Amortization expense	(25,600)	$ (24,300)
Balance at end of period	$ 90,706