Accumulated Other Comprehensive Income Loss - Reclassifications from AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains (losses)	$ 165	$ (30)
Net Investment Income	470	451
Income from continuing operations, before tax	775	519
Income tax expense	145	91
Income from discontinued operations, net of tax	0	169
Insurance operating costs and other expenses	1,048	1,037
Net income	630	597
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	9	(23)
Net Unrealized Gain on Securities | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains (losses)	21	(38)
Income from continuing operations, before tax	21	(38)
Income tax expense	4	(8)
Income from discontinued operations, net of tax		3
Net income	17	(27)
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	1	9
Income tax expense	0	2
Income from discontinued operations, net of tax		6
Net income	1	13
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
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 (losses)		1
Net Investment Income		8
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	1	1
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)	(13)
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	(11)	(12)
Income tax expense	(2)	(3)
Net income	$ (9)	$ (9)