Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract period	4 years
Service fee receivable, net	$ 5,246	$ 3,434
Service fee and commission income recognized during the period	$ 7,900

Carrying amount as of the balance sheet date, net of allowance for doubtful accounts, of all premiums and other types of receivables due from other persons or entities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.5)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Name:	us-gaap_PremiumsAndOtherReceivablesNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant