Revenue - Summary (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue
Revenue	$ 122,363	$ 144,758	$ 356,398	$ 413,931
Direct
Revenue
Revenue	74,408		218,494
Tech-enabled
Revenue
Revenue	39,872		113,419
Traditional
Revenue
Revenue	8,083		24,485
North America
Revenue
Revenue	75,022	79,487	222,643	232,687
North America | Direct
Revenue
Revenue	38,025		113,246
North America | Tech-enabled
Revenue
Revenue	28,914		84,912
North America | Traditional
Revenue
Revenue	8,083		24,485
Europe
Revenue
Revenue	47,341	65,271	133,755	181,244
Europe | Direct
Revenue
Revenue	36,383		105,248
Europe | Tech-enabled
Revenue
Revenue	$ 10,958		$ 28,507
Presented without adoption of ASC 606
Revenue
Revenue		144,758		413,931
Presented without adoption of ASC 606 | Direct
Revenue
Revenue		92,331		259,471
Presented without adoption of ASC 606 | Tech-enabled
Revenue
Revenue		42,741		124,268
Presented without adoption of ASC 606 | Traditional
Revenue
Revenue		9,686		30,192
Presented without adoption of ASC 606 | North America
Revenue
Revenue		79,487		232,687
Presented without adoption of ASC 606 | North America | Direct
Revenue
Revenue		40,946		117,738
Presented without adoption of ASC 606 | North America | Tech-enabled
Revenue
Revenue		28,855		84,757
Presented without adoption of ASC 606 | North America | Traditional
Revenue
Revenue		9,686		30,192
Presented without adoption of ASC 606 | Europe
Revenue
Revenue		65,271		181,244
Presented without adoption of ASC 606 | Europe | Direct
Revenue
Revenue		51,385		141,733
Presented without adoption of ASC 606 | Europe | Tech-enabled
Revenue
Revenue		$ 13,886		$ 39,511