Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
U.S. statutory tax rate	21.00%	35.00%	35.00%
Unrecognized tax benefits	$ 0	$ 0	$ 0
Foreign
Income Taxes [Line Items]
Operating loss carryforwards	31,566
Deferred tax assets for foreign operating loss carryforwards	8,397
Operating loss carryforwards with indefinite life	28,714
Deferred tax assets for operating loss carryforwards for indefinite life	7,658
Operating loss carryforwards which expire between 2019 and 2026	2,852
Deferred tax assets for operating loss carryforwards which expire between 2019 and 2026	739
Group LP
Income Taxes [Line Items]
Net deferred tax asset increase	168,859
Deferred tax assets attributable to exchanges by partners	$ 171,506
Percentage of cash distribution to partners in connection to IPO attributable to exchanges by partners, payable to partners	85.00%
Total tax receivable agreement obligation	$ 145,780
Period of tax receivable agreement	15 years