Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Investment Income [Line Items]
Gross investment income	$ 1,034	$ 978	$ 2,694	$ 2,834
Less: Investment expenses	38	50	130	153
Net investment income	996	928	2,564	2,681
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	676	665	2,021	1,997
Equity securities
Net Investment Income [Line Items]
Gross investment income	1	2	4	6
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	166	172	498	507
Policy loans
Net Investment Income [Line Items]
Gross investment income	15	18	40	51
Limited partnerships and LLCs
Net Investment Income [Line Items]
Gross investment income	155	79	48	175
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Gross investment income	7	30	44	67
Other
Net Investment Income [Line Items]
Gross investment income	$ 14	$ 12	$ 39	$ 31