Equity (Reclassifications Out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment gains (losses)	$ (42)	$ 21	$ (120)	$ (34)
Net derivative gains (losses)	(665)	(162)	(1,230)	(1,064)
Net investment income	828	732	2,400	2,231
Income (loss) from continuing operations before provision for income tax	(407)	(122)	(660)	(1,187)
Provision for income tax expense (benefit)	108	(567)	195	(131)
Net income (loss)	(299)	(689)	(465)	(1,318)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	6	21	(54)	(26)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Investment Gains (Losses), Net of Related Offsets
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net investment gains (losses)	(36)	24	(136)	(22)
Net derivative gains (losses)	(1)	0	(1)	(44)
Net investment income	0	(1)	1	1
Income (loss) from continuing operations before provision for income tax	(37)	23	(136)	(65)
Provision for income tax expense (benefit)	8	(2)	31	31
Net income (loss)	(29)	21	(105)	(34)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before provision for income tax	46	1	65	13
Provision for income tax expense (benefit)	(11)	(1)	(14)	(5)
Net income (loss)	35	0	51	8
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Derivatives | Interest rate swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net derivative gains (losses)	15	0	31	0
Net investment income	0	0	2	2
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Derivatives | Interest rate forwards
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net derivative gains (losses)	30	0	31	0
Net investment income	1	1	2	2
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Derivatives | Foreign currency swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net derivative gains (losses)	$ 0	$ 0	$ (1)	$ 9