Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Financial assets:
Mortgage loans		$ 1,475	$ 1,329
Policy loans		158	164
Financial liabilities:
Long-term debt		1,912	1,473
Level 1
Financial assets:
Cash and cash equivalents		2,698	2,314
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		2,698	2,314
Financial liabilities:
Annuity benefits accumulated	[1]	0	0
Long-term debt		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
Policy loans		0	0
Total financial assets not accounted for at fair value		0	0
Financial liabilities:
Annuity benefits accumulated	[1]	0	0
Long-term debt		2,057	1,619
Total financial liabilities not accounted for at fair value		2,057	1,619
Level 3
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		1,492	1,346
Policy loans		158	164
Total financial assets not accounted for at fair value		1,650	1,510
Financial liabilities:
Annuity benefits accumulated	[1]	42,462	40,182
Long-term debt		3	3
Total financial liabilities not accounted for at fair value		42,465	40,185
Carrying Value
Financial assets:
Cash and cash equivalents		2,698	2,314
Mortgage loans		1,475	1,329
Policy loans		158	164
Total financial assets not accounted for at fair value		4,331	3,807
Financial liabilities:
Annuity benefits accumulated	[1]	41,137	40,159
Long-term debt		1,912	1,473
Total financial liabilities not accounted for at fair value		43,049	41,632
Fair Value
Financial assets:
Cash and cash equivalents		2,698	2,314
Mortgage loans		1,492	1,346
Policy loans		158	164
Total financial assets not accounted for at fair value		4,348	3,824
Financial liabilities:
Annuity benefits accumulated	[1]	42,462	40,182
Long-term debt		2,060	1,622
Total financial liabilities not accounted for at fair value		$ 44,522	$ 41,804

[1] Excludes $255 million and $247 million of life contingent annuities in the payout phase at June 30, 2020 and December 31, 2019, respectively.