Revenue - Opening and Closing Balances (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 746,571	$ 630,119	$ 630,119
Increase (decrease) in accounts receivables	116,452
Contract asset, current	9,491	9,778
Increase (decrease) in contract asset, current	(287)
Contract asset, non-current	25,685	16,396
Increase (decrease) in contract asset, non-current	9,289
Deferred revenue, current	76,892	73,142
Increase (decrease) in deferred revenue, current	3,750
Deferred revenue, non-current	46,798	$ 46,641
Increase (decrease) in deferred revenue, non-current	$ 157