Changes in and Reclassifications From Accumulated Other Comprehensive Income (Loss) - Reclassification from AOCI (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains (losses)									$ 398	$ (111)	$ 173
Net investment income									1,951	1,780	1,603
Interest Expense									259	298	316
Insurance operating costs and other expenses									4,580	4,281	4,563
Income from continuing operations before income taxes									2,560	1,753	723
Income tax expense									475	268	985
Income (loss) from discontinued operations, net of tax, available to common stockholders									0	322	(2,869)
Net income (loss)	$ 548	$ 535	$ 372	$ 630	$ 196	$ 432	$ 582	$ 597	2,085	1,807	(3,131)
Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)									111	(69)	(269)
Net Unrealized Gain on Securities | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains (losses)									174	(80)	152
Income from continuing operations before income taxes									174	(80)	152
Income tax expense									37	(17)	53
Income (loss) from discontinued operations, net of tax, available to common stockholders									0	(2)	103
Net income (loss)									137	(65)	202
OTTI Losses in OCI | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains (losses)									0	0	0
Income from continuing operations before income taxes									0	0	0
Income tax expense									0	0	0
Income (loss) from discontinued operations, net of tax, available to common stockholders									0	1	0
Net income (loss)									0	1	0
Net Gain (Loss) on Cash Flow Hedging Instruments | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations before income taxes									10	36	42
Income tax expense									2	8	15
Income (loss) from discontinued operations, net of tax, available to common stockholders									0	5	23
Net income (loss)									8	33	50
Net Gain (Loss) on Cash Flow Hedging Instruments | Amount Reclassified from AOCI | Interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains (losses)									2	6	5
Net investment income									4	30	37
Interest Expense									1	0	0
Net Gain (Loss) on Cash Flow Hedging Instruments | Amount Reclassified from AOCI | Foreign currency swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment income									3	0	0
Amortization of prior service credit | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Insurance operating costs and other expenses									7	7	7
Amortization of actuarial loss | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Insurance operating costs and other expenses									(50)	(55)	(61)
Settlement loss | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Insurance operating costs and other expenses									0	0	(747)
Pension and Other Postretirement Plan Adjustments | Amount Reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations before income taxes									(43)	(48)	(801)
Income tax expense									(9)	(10)	(280)
Net income (loss)									$ (34)	$ (38)	$ (521)