Revenue from Contracts with Customers - Additional Information (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Bad debt expense	$ 0	$ 0
Contract assets	0	0
Contract liabilities	0	0
Deferred contract costs	0	0
Revenue recognized from performance obligations related to prior periods	0	0
Transaction fees
Disaggregation of Revenue [Line Items]
Accounts receivable	0	0
Management fees, SMAs and referral fees
Disaggregation of Revenue [Line Items]
Accounts receivable	$ 400	$ 400