Investments (Fixed Maturity Securities by Sector) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	$ 66,992	$ 63,083
Fixed maturity securities, allowance for credit losses	3	0
Fixed maturity securities, gross unrealized gains	11,429	7,060
Fixed maturity securities, gross unrealized losses	279	166
Fixed maturity securities, estimated fair value	78,139	69,977
U.S. Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	30,759	27,841
Fixed maturity securities, allowance for credit losses	2	0
Fixed maturity securities, gross unrealized gains	4,669	2,815
Fixed maturity securities, gross unrealized losses	132	65
Fixed maturity securities, estimated fair value	35,294	30,591
Foreign Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	9,553	9,017
Fixed maturity securities, allowance for credit losses	1	0
Fixed maturity securities, gross unrealized gains	1,063	736
Fixed maturity securities, gross unrealized losses	100	67
Fixed maturity securities, estimated fair value	10,515	9,686
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	7,727	8,600
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	652	440
Fixed maturity securities, gross unrealized losses	9	10
Fixed maturity securities, estimated fair value	8,370	9,030
U.S. Government and Agency
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	5,574	5,396
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	3,179	1,848
Fixed maturity securities, gross unrealized losses	0	0
Fixed maturity securities, estimated fair value	8,753	7,244
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	5,778	5,460
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	563	263
Fixed maturity securities, gross unrealized losses	9	9
Fixed maturity securities, estimated fair value	6,332	5,714
State and Political Subdivision
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	3,413	3,326
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	935	687
Fixed maturity securities, gross unrealized losses	2	2
Fixed maturity securities, estimated fair value	4,346	4,011
ABS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	2,676	1,940
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	55	21
Fixed maturity securities, gross unrealized losses	21	11
Fixed maturity securities, estimated fair value	2,710	1,950
Foreign Government
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	1,512	1,503
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	313	250
Fixed maturity securities, gross unrealized losses	6	2
Fixed maturity securities, estimated fair value	$ 1,819	$ 1,751

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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