Accumulated Other Comprehensive Income (Loss) - Changes in AOCI, including Reclassification Adjustments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components Of Accumulated Other Comprehensive Income Loss [Line Items]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ 0	$ 9	$ (5)
Available-for-sale securities, Before-Tax Amount:
Net unrealized gains/losses on securities	1,995
Other	0	(5)	5
Adjustments for amounts recognized in Net realized capital gains (losses) in the Consolidated Statements of Operations	(11)	69	29
DAC/VOBA and Sales inducements	(479)	360	(109)
Premium deficiency reserve adjustment	(160)	64	(25)
Change in unrealized gains/losses on available-for-sale securities	1,346	(905)	460
Available-for-sale securities, Income Tax:
Net unrealized gains/losses on securities	(419)
Other	0	1	(2)
Adjustments for amounts recognized in Net realized capital gains (losses) in the Consolidated Statements of Operations	2	(14)	(10)
DAC/VOBA and Sales inducements	100	(76)	42
Premium deficiency reserve adjustment	33	(13)	9
Change in unrealized gains/losses on available-for-sale securities	(284)	195	(150)
Available-for-sale securities, After-Tax Amount:
Net unrealized gains/losses on securities	1,576
Other	0	(4)	3
Adjustments for amounts recognized in Net realized capital gains (losses) in the Consolidated Statements of Operations	(9)	55	19
DAC/VOBA and Sales inducements	(379)	284	(67)
Premium deficiency reserve adjustment	(127)	51	(16)
Change in unrealized gains/losses on available-for-sale securities	1,062	(710)	310
Derivatives, Before-Tax Amount:
Derivatives	1	40	(53)
Adjustments related to effective cash flow hedges for amounts recognized in Net investment income in the Consolidated Statements of Operations	(23)	(24)	(24)
Change in unrealized gains/losses on derivatives	(22)	16	(77)
Derivatives, Income Tax:
Derivatives	0	(8)	19
Adjustments related to effective cash flow hedges for amounts recognized in Net investment income in the Consolidated Statements of Operations	5	5	8
Change in unrealized gains/losses on derivatives	5	(3)	27
Derivatives, After-Tax Amount:
Derivatives	1	32	(34)
Adjustments related to effective cash flow hedges for amounts recognized in Net investment income in the Consolidated Statements of Operations	(18)	(19)	(16)
Change in unrealized gains/losses on derivatives	(17)	13	(50)
OTTI:
Other-than-temporary impairments	1	8	(4)
Change in OTTI, Income Tax	0	(2)	1
Change in OTTI, After-Tax Amount	1	6	(3)
Pension and other post-employment benefit liability, Before-Tax Amount:
Amortization of prior service cost recognized in Operating expenses in the Consolidated Statements of Operations	(1)	(1)	(2)
Change in pension and other postretirement benefits liability	(1)	(1)	(2)
Other comprehensive income (loss), before tax	1,323	(890)	381
Pension and other post-employment benefit liability, Income Tax:
Amortization of prior service cost recognized in Operating expenses in the Consolidated Statements of Operations	3	0	1
Change in pension and other postretirement benefits liability	3	0	1
Other comprehensive income (loss)	(276)	192	(122)
Pension and other post-employment benefit liability, After-Tax Amount:
Amortization of prior service cost recognized in Operating expenses in the Consolidated Statements of Operations	2	(1)	(1)
Change in pension and other postretirement benefits liability	2	(1)	(1)
Other comprehensive income (loss), after tax	1,047	(698)	259
Fixed maturities
Available-for-sale securities, Before-Tax Amount:
Net unrealized gains/losses on securities		(1,401)	564
Available-for-sale securities, Income Tax:
Net unrealized gains/losses on securities		299	(190)
Available-for-sale securities, After-Tax Amount:
Net unrealized gains/losses on securities		(1,102)	374
Deferred Tax Asset, Capital Loss Carryforward
Pension and other post-employment benefit liability, After-Tax Amount:
Increase (decrease) in valuation allowance	$ 0	$ 9	$ 0