Investments - Mortgage Loans, Loan to Value Ratio (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage loans, net of allowances	$ 17,385	$ 15,938
Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,043	1,913
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,529	1,478
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,010	130
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,675	1,012
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,429	2,662
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,982	4,420
Mortgage loans, net of allowances	12,496	11,448
Mortgage loans, before allowance for credit losses	12,668	11,615
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,027	1,807
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,529	1,478
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,010	130
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,572	1,012
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,398	2,563
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,849	4,393
Mortgage loans, before allowance for credit losses	12,385	11,383
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development \| Less than 50%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	252	431
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,140	1,153
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	151	44
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	201	152
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	606	201
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	453	600
Mortgage loans, before allowance for credit losses	2,803	2,581
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development \| 50% to 60%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	67	315
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	196	147
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	325	40
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	715	300
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,332	765
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	291	1,320
Mortgage loans, before allowance for credit losses	2,926	2,887
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development \| 61% to 70%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	595	583
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	138	106
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	440	46
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,282	440
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,990	1,222
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	646	1,988
Mortgage loans, before allowance for credit losses	5,091	4,385
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development \| 71% to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	113	478
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	18	13
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	94	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	374	95
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	470	375
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	459	485
Mortgage loans, before allowance for credit losses	1,528	1,446
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development \| 81% to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year		21
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year		25
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year		0
Mortgage loans, before allowance for credit losses		46
Commercial mortgage loans \| Commercial mortgage loans, excluding loans under development \| 100% or greater
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	37	38
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Mortgage loans, before allowance for credit losses	$ 37	$ 38

Amount of financing receivable originated more than five years prior to current fiscal year.

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Amount of financing receivable originated in current fiscal year.

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Amount of financing receivable originated in fiscal year prior to current fiscal year.

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Amount of financing receivable originated three years prior to current fiscal year.

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Amount of financing receivable originated two years prior to current fiscal year.

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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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Amount, before allowance for credit loss, of financing receivable.

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