Supplemental Information - Schedule of Revenues by Geographic Region (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenues From External Customers And Long Lived Assets [Line Items]
Net revenues	$ 64,756	$ 50,109	$ 178,395	$ 123,365	$ 177,026
Germany
Revenues From External Customers And Long Lived Assets [Line Items]
Net revenues	$ 17,536	$ 14,664	$ 48,545	$ 26,880	$ 40,215