Revenues and Business Information - Schedule of Geographical Distribution of Revenues and Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	$ 137,783	$ 219,418
Total assets	681,690		$ 914,375
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	122,680	178,682
Total assets	551,623		756,053
Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	6,716	23,436
Total assets	38,668		55,064
Rest of World
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	8,387	$ 17,300
Total assets	$ 91,399		$ 103,258