Borrowings - Repurchase agreements accounted for as secured borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets Sold under Agreements to Repurchase
Repurchase liability	$ 106,028	$ 193,378
Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	106,028	193,378
US Treasury Securities \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	101,954	191,245
US Treasury Securities \| Within 30 days \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	14,861	88,646
US Treasury Securities \| After 30 to 90 days \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	14,636	78,061
US Treasury Securities \| After 90 days \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	72,457	24,538
Mortgage Backed Securities \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	3,248	1,235
Mortgage Backed Securities \| Within 30 days \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	2,961	1,235
Mortgage Backed Securities \| After 90 days \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	287	0
CMO \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	826	898
CMO \| Within 30 days \| Secured Debt
Assets Sold under Agreements to Repurchase
Repurchase liability	$ 826	$ 898

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant