Fair value of financial assets and liabilities - Financial assets and liabilities measured at fair value (Details) - Recurring - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Fair value of financial assets and liabilities
Assets at fair value	$ 0	$ 0
Liabilities at fair value	$ 0	$ 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