Investments (Mortgage Loans in Nonaccrual Status by Portfolio Segment) (Details) - Mortgage Loans - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Nonaccrual [Line Items]
Financing receivable in nonaccrual status	$ 41	$ 58
Commercial
Financing Receivable, Nonaccrual [Line Items]
Financing receivable in nonaccrual status	0	0
Agricultural
Financing Receivable, Nonaccrual [Line Items]
Financing receivable in nonaccrual status	1	21
Residential
Financing Receivable, Nonaccrual [Line Items]
Financing receivable in nonaccrual status	$ 40	$ 37

Amount of financing receivable on nonaccrual status.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant