Accumulated Other Comprehensive Income - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense (benefit)	$ 17	$ (45)	$ 309	$ (324)
Other comprehensive income (loss), after tax	(83)	102	(1,330)	795
Adoption of ASU 2016-01					$ (3)
Change in Accumulated Other Comprehensive Income	(83)	102	(1,372)	795
Unrealized investment gains (losses) on AFS securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	(174)	249	(2,345)	1,500
DAC, DSI, VOBA, and future policy benefit adjustment on AFS securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	77	(61)	701	(284)
Unrealized gains (losses) on AFS securities, including DAC, DSI, VOBA, and future policy benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment for gains (losses) realized in net income	6	17	36	44
Income tax expense (benefit)	(18)	55	(319)	347
Other comprehensive income (loss), after tax	(85)	116	(1,361)	825
Noncredit component of OTTI losses on AFS securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	(4)	(7)	(4)	(5)
Reclassification adjustment for gains (losses) realized in net income	0	(9)	0	(7)
Income tax expense (benefit)	1	(1)	(1)	1
Other comprehensive income (loss), after tax	(3)	1	(3)	1
Unrealized gains (losses) on hedging instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	7	(31)	52	(69)
Income tax expense (benefit)	2	(11)	11	(24)
Other comprehensive income (loss), after tax	5	(20)	41	(45)
Pension adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	0	1	3	0
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), after tax	$ 0	$ 4	$ (10)	$ 14
Accounting Standards Update 2016-01 [Member] | AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Adoption of ASU 2016-01					$ (42)