Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Financial assets:
Mortgage loans	$ 408	$ 377
Long-term debt	1,963	1,963
Cash and cash equivalents from discontinued operations	636		$ 368
Annuity subsidiaries | Assets of discontinued annuity operations
Financial assets:
Cash and cash equivalents from discontinued operations	636	1,145
Level 1
Financial assets:
Cash and cash equivalents	1,691	1,665
Mortgage loans	0	0
Total financial assets not accounted for at fair value	1,691	1,665
Long-term debt	0	0
Total financial liabilities not accounted for at fair value	0	0
Level 1 | Annuity subsidiaries | Assets of discontinued annuity operations
Financial assets:
Cash and cash equivalents	636	1,145
Mortgage loans	0	0
Policy loans	0	0
Total financial assets not accounted for at fair value	636	1,145
Level 1 | Annuity subsidiaries | Liabilities of discontinued annuity operations
Financial assets:
Annuity benefits accumulated	0	0
Total financial liabilities not accounted for at fair value	0	0
Level 2
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	0	0
Total financial assets not accounted for at fair value	0	0
Long-term debt	2,215	2,322
Total financial liabilities not accounted for at fair value	2,215	2,322
Level 2 | Annuity subsidiaries | Assets of discontinued annuity operations
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	0	0
Policy loans	0	0
Total financial assets not accounted for at fair value	0	0
Level 2 | Annuity subsidiaries | Liabilities of discontinued annuity operations
Financial assets:
Annuity benefits accumulated	0	0
Total financial liabilities not accounted for at fair value	0	0
Level 3
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	411	382
Total financial assets not accounted for at fair value	411	382
Long-term debt	3	3
Total financial liabilities not accounted for at fair value	3	3
Level 3 | Annuity subsidiaries | Assets of discontinued annuity operations
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	1,262	1,270
Policy loans	148	151
Total financial assets not accounted for at fair value	1,410	1,421
Level 3 | Annuity subsidiaries | Liabilities of discontinued annuity operations
Financial assets:
Annuity benefits accumulated	42,360	43,081
Total financial liabilities not accounted for at fair value	42,360	43,081
Carrying Value
Financial assets:
Cash and cash equivalents	1,691	1,665
Mortgage loans	408	377
Total financial assets not accounted for at fair value	2,099	2,042
Long-term debt	1,963	1,963
Total financial liabilities not accounted for at fair value	1,963	1,963
Carrying Value | Annuity subsidiaries | Assets of discontinued annuity operations
Financial assets:
Total financial assets not accounted for at fair value	2,028	2,547
Carrying Value | Annuity subsidiaries | Liabilities of discontinued annuity operations
Financial assets:
Annuity benefits accumulated	41,760	41,460
Total financial liabilities not accounted for at fair value	41,760	41,460
Fair Value
Financial assets:
Cash and cash equivalents	1,691	1,665
Mortgage loans	411	382
Total financial assets not accounted for at fair value	2,102	2,047
Long-term debt	2,218	2,325
Total financial liabilities not accounted for at fair value	2,218	2,325
Fair Value | Annuity subsidiaries | Assets of discontinued annuity operations
Financial assets:
Cash and cash equivalents	636	1,145
Mortgage loans	1,262	1,270
Policy loans	148	151
Total financial assets not accounted for at fair value	2,046	2,566
Fair Value | Annuity subsidiaries | Liabilities of discontinued annuity operations
Financial assets:
Annuity benefits accumulated	42,360	43,081
Total financial liabilities not accounted for at fair value	$ 42,360	$ 43,081