Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Foreign exchange gains	$ 30	$ 500
Deferred revenue contract liability	$ 76,100			$ 30,600
Performance obligation timing	We expect to recognize substantially all of these amounts in revenues within approximately 12 months.
Deferred revenue recognized	$ 16,200
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Derivative term of contract			1 year
Sales Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Consolidated revenues, net (percent)	100.00%	100.00%
Contracts with customers | Sales Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Consolidated revenues, net (percent)	80.00%
Intra-entity Transactions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Foreign exchange gains	$ 77,000	$ 24,400