Investments (Fixed Maturity Securities by Sector) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	$ 64,182	$ 63,083
Fixed maturity securities, allowance for credit losses	10	0
Fixed maturity securities, gross unrealized gains	7,580	7,060
Fixed maturity securities, gross unrealized losses	1,550	166
Fixed maturity securities, estimated fair value	70,202	69,977
U.S. Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	28,604	27,841
Fixed maturity securities, allowance for credit losses	8	0
Fixed maturity securities, gross unrealized gains	2,319	2,815
Fixed maturity securities, gross unrealized losses	791	65
Fixed maturity securities, estimated fair value	30,124	30,591
Foreign Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	9,180	9,017
Fixed maturity securities, allowance for credit losses	1	0
Fixed maturity securities, gross unrealized gains	350	736
Fixed maturity securities, gross unrealized losses	428	67
Fixed maturity securities, estimated fair value	9,101	9,686
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	8,319	8,600
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	545	440
Fixed maturity securities, gross unrealized losses	51	10
Fixed maturity securities, estimated fair value	8,813	9,030
U.S. Government and Agency
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	5,530	5,396
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	3,214	1,848
Fixed maturity securities, gross unrealized losses	0	0
Fixed maturity securities, estimated fair value	8,744	7,244
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	5,533	5,460
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	224	263
Fixed maturity securities, gross unrealized losses	79	9
Fixed maturity securities, estimated fair value	5,678	5,714
State and Political Subdivision
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	3,344	3,326
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	733	687
Fixed maturity securities, gross unrealized losses	4	2
Fixed maturity securities, estimated fair value	4,073	4,011
ABS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	2,165	1,940
Fixed maturity securities, allowance for credit losses	0	0
Fixed maturity securities, gross unrealized gains	13	21
Fixed maturity securities, gross unrealized losses	156	11
Fixed maturity securities, estimated fair value	2,022	1,950
Foreign Government
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	1,507	1,503
Fixed maturity securities, allowance for credit losses	1	0
Fixed maturity securities, gross unrealized gains	182	250
Fixed maturity securities, gross unrealized losses	41	2
Fixed maturity securities, estimated fair value	$ 1,647	$ 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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