Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Financial assets:
Mortgage loans		$ 1,346	$ 1,329
Policy loans		161	164
Financial liabilities:
Long-term debt		1,473	1,473
Level 1
Financial assets:
Cash and cash equivalents		1,673	2,314
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		1,673	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		1,408	1,619
Total financial liabilities not accounted for at fair value		1,408	1,619
Level 3
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		1,350	1,346
Policy loans		161	164
Total financial assets not accounted for at fair value		1,511	1,510
Financial liabilities:
Annuity benefits accumulated	[1]	39,773	40,182
Long-term debt		3	3
Total financial liabilities not accounted for at fair value		39,776	40,185
Carrying Value
Financial assets:
Cash and cash equivalents		1,673	2,314
Mortgage loans		1,346	1,329
Policy loans		161	164
Total financial assets not accounted for at fair value		3,180	3,807
Financial liabilities:
Annuity benefits accumulated	[1]	40,218	40,159
Long-term debt		1,473	1,473
Total financial liabilities not accounted for at fair value		41,691	41,632
Fair Value
Financial assets:
Cash and cash equivalents		1,673	2,314
Mortgage loans		1,350	1,346
Policy loans		161	164
Total financial assets not accounted for at fair value		3,184	3,824
Financial liabilities:
Annuity benefits accumulated	[1]	39,773	40,182
Long-term debt		1,411	1,622
Total financial liabilities not accounted for at fair value		$ 41,184	$ 41,804

[1] Excludes $245 million and $247 million of life contingent annuities in the payout phase at March 31, 2020 and December 31, 2019, respectively.