Investments, Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions		Mar. 31, 2020		Dec. 31, 2019
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		$ 38,059		$ 38,157
Gross unrealized gains		3,231		4,128
Gross unrealized losses		1,117		45
Allowance for credit loss		49	[1]	0
Estimated fair value		40,124		42,240
Unrealized OTTI losses (gains)	[1]			(19)
Shadow adjustments		1,500		2,000
Fixed Maturities Available-for-Sale [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		38,019		38,106
Gross unrealized gains		3,230		4,126
Gross unrealized losses		1,117		45
Allowance for credit loss	[1]	49
Estimated fair value		40,083		42,187
Unrealized OTTI losses (gains)	[1]			(19)
Corporate and Other Bonds [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		20,181		19,789
Gross unrealized gains		1,419		2,292
Gross unrealized losses		817		32
Allowance for credit loss		49	[1]	0
Estimated fair value		20,734		22,049
States, Municipalities and Political Subdivisions [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		8,957		9,093
Gross unrealized gains		1,536		1,559
Gross unrealized losses		2
Estimated fair value		10,491		10,652
Asset-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		8,273		8,577
Gross unrealized gains		252		260
Gross unrealized losses		294		10
Allowance for credit loss	[1]	0
Estimated fair value		8,231		8,827
Unrealized OTTI losses (gains)	[1]			(19)
Residential Mortgage-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		4,198		4,387
Gross unrealized gains		207		133
Gross unrealized losses		8		1
Estimated fair value		4,397		4,519
Unrealized OTTI losses (gains)	[1]			(17)
Commercial Mortgage-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		2,207		2,265
Gross unrealized gains		36		86
Gross unrealized losses		153		5
Estimated fair value		2,090		2,346
Unrealized OTTI losses (gains)	[1]			1
Other Asset-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		1,868		1,925
Gross unrealized gains		9		41
Gross unrealized losses		133		4
Estimated fair value		1,744		1,962
Unrealized OTTI losses (gains)	[1]			(3)
U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		147		146
Gross unrealized gains		8		1
Gross unrealized losses				2
Estimated fair value		155		145
Foreign Government [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		452		491
Gross unrealized gains		15		14
Gross unrealized losses		4		1
Estimated fair value		463		504
Redeemable Preferred Stock [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		9		10
Estimated fair value		9		10
Fixed Maturities Trading [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		40		51
Gross unrealized gains		1		2
Estimated fair value		$ 41		$ 53

[1] On January 1, 2020, the Company adopted ASU 2016-13; see Note 1. The Unrealized OTTI Losses (Gains) column that tracked subsequent valuation changes on securities for which a credit loss had previously been recorded has been replaced with the Allowance for Credit Losses column. Prior period amounts were not adjusted for the adoption of this standard.