Contracts Accounted for as Credit Derivatives - Collateral Posting Requirements (Details) $ in Millions	Dec. 31, 2019 USD ($) Counterparty
Collateral Debt Obligations, Credit Derivative Contracts, Gross Par with Collateral Posting Requirements [Member]
Credit Derivatives
Derivative, number of counterparties \| Counterparty	1
Derivative, notional amount	$ 180
Collateral Debt Obligations, Maximum Posting Requirement [Member]
Credit Derivatives
Derivative, notional amount	$ 180

Nominal or face amount used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant