Accumulated Other Comprehensive Income Loss - Reclassifications from AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains	$ 90	$ 39	$ 335	$ 61
Income from continuing operations, before tax	653	530	1,884	1,586
Income tax expense	118	103	347	297
Income from discontinued operations, net of tax	0	5	0	322
Net Investment Income	490	444	1,448	1,323
Interest Expense	67	69	194	228
Insurance operating costs and other expenses	1,167	1,091	3,356	3,195
Net income	535	432	1,537	1,611
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	51	(15)	93	(52)
Net Unrealized Gain on Securities | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains	72	(15)	143	(59)
Income from continuing operations, before tax	72	(15)	143	(59)
Income tax expense	15	(3)	30	(12)
Income from discontinued operations, net of tax		0		(2)
Net income	57	(12)	113	(49)
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains		0		0
Income from continuing operations, before tax		0		0
Income tax expense		0		0
Income from discontinued operations, net of tax		0		1
Net income		0		1
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations, before tax	2	7	6	25
Income tax expense	0	1	1	5
Income from discontinued operations, net of tax		0		5
Net income	2	6	5	25
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income | Currency Swap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Investment Income	1		2
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income | Interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains	0	0	2	1
Net Investment Income	1	7	1	24
Interest Expense	0		1
Amortization of prior service credit | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Insurance operating costs and other expenses	2	2	5	5
Amortization of actuarial loss | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Insurance operating costs and other expenses	(12)	(14)	(37)	(42)
Pension and Other Postretirement Plan Adjustments | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from continuing operations, before tax	(10)	(12)	(32)	(37)
Income tax expense	(2)	(3)	(7)	(8)
Net income	$ (8)	$ (9)	$ (25)	$ (29)