Investments (Details) - Fixed Maturities - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investment disclosure details
Fixed maturities, amortized cost	$ 68,830	$ 65,281
Allowance for expected credit losses	2	0
Gross unrealized gains	5,186	2,882
Gross unrealized losses	11	29
Fixed maturities, at fair value	74,003	68,134
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	2,111	2,076
Allowance for expected credit losses	0
Gross unrealized gains	38	19
Gross unrealized losses	0	0
Fixed maturities, at fair value	2,149	2,095
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	33,763	28,356
Allowance for expected credit losses	0
Gross unrealized gains	2,599	1,567
Gross unrealized losses	2	6
Fixed maturities, at fair value	36,360	29,917
Obligations of states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	17,289	15,490
Allowance for expected credit losses	0
Gross unrealized gains	1,370	829
Gross unrealized losses	2	4
Fixed maturities, at fair value	18,657	16,315
Obligations of states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	11,806	9,731
Allowance for expected credit losses	0
Gross unrealized gains	909	586
Gross unrealized losses	0	2
Fixed maturities, at fair value	12,715	10,315
Obligations of states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,343	1,167
Allowance for expected credit losses	0
Gross unrealized gains	101	64
Gross unrealized losses	0	0
Fixed maturities, at fair value	1,444	1,231
Obligations of states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	3,325	1,968
Allowance for expected credit losses	0
Gross unrealized gains	219	88
Gross unrealized losses	0	0
Fixed maturities, at fair value	3,544	2,056
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,028	1,167
Allowance for expected credit losses	0
Gross unrealized gains	26	8
Gross unrealized losses	0	2
Fixed maturities, at fair value	1,054	1,173
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	2,222	3,192
Allowance for expected credit losses	0	0
Gross unrealized gains	139	91
Gross unrealized losses	0	3
Fixed maturities, at fair value	2,361	3,280
All other corporate bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	29,683	30,442
Allowance for expected credit losses	2	0
Gross unrealized gains	2,382	1,195
Gross unrealized losses	9	18
Fixed maturities, at fair value	32,054	31,619
Redeemable preferred stock [Member]
Investment disclosure details
Fixed maturities, amortized cost	23	48
Allowance for expected credit losses	0
Gross unrealized gains	2	2
Gross unrealized losses	0	0
Fixed maturities, at fair value	$ 25	$ 50

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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