Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair Value Measurement [Line Items]
Transfers between fair value measure levels	$ 0	$ 0
Convertible Preferred Stock
Fair Value Measurement [Line Items]
Financial liabilities fair value disclosure	$ 0

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

No definition available.

Name:	us-gaap_FinancialLiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant