Revenue - Opening and Closing Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 752,680	$ 630,119	$ 630,119
Increase (decrease) in accounts receivables	122,561
Contract asset, current	9,346	9,778
Increase (decrease) in contract asset, current	(432)
Contract asset, non-current	18,883	16,396
Increase (decrease) in contract asset, non-current	2,487
Deferred revenue, current	77,026	73,142
Increase (decrease) in deferred revenue, current	3,884
Deferred revenue, non-current	46,517	$ 46,641
Increase (decrease) in deferred revenue, non-current	$ (124)