Other Assets Other Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Other Assets [Line Items]
Accumulated amortization of costs to obtain contracts	$ (27,641)		$ (24,992)
Unbilled receivables	90,578		81,703
Operating lease right-of-use assets	38,051		20,257
Other assets	31,915		39,410
Other assets, total	367,951		335,685
Amortization cost	2,700	$ 1,900
Customer agreements
Other Assets [Line Items]
Costs to obtain contracts- customer agreements	232,567		219,307
Incentives
Other Assets [Line Items]
Costs to obtain contracts- customer agreements	$ 2,481		$ 0