Changes in and Reclassifications From Accumulated Other Comprehensive Income (Loss) - AOCI Rollforward (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	May 31, 2018	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	$ (88)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	13,494	$ 13,101	$ 13,494
OCI, net of tax		1,631	(2,237)	$ 1,000
Ending balance		16,270	13,101	13,494
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax				273
Adjusted balance beginning of period				2,204
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,931	24	1,931	1,276
OCI before reclassifications		1,797	(2,245)	857
Amounts reclassified from AOCI		(137)	65	(202)
OCI, net of tax		1,660	(2,180)	655
Ending balance		1,684	24	1,931
OTTI Losses in OCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax				0
Adjusted balance beginning of period				(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(3)	(4)	(3)	(3)
OCI before reclassifications		1	0	0
Amounts reclassified from AOCI		0	(1)	0
OCI, net of tax		1	(1)	0
Ending balance		(3)	(4)	(3)
Net Gain (Loss) on Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax				2
Adjusted balance beginning of period				20
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	18	(5)	18	76
OCI before reclassifications		22	8	(8)
Amounts reclassified from AOCI		(8)	(33)	(50)
OCI, net of tax		14	(25)	(58)
Ending balance		9	(5)	18
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax				4
Adjusted balance beginning of period				38
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	34	30	34	6
OCI before reclassifications		4	(8)	28
Amounts reclassified from AOCI		0	0	0
OCI, net of tax		4	(8)	28
Ending balance		34	30	34
Pension and Other Postretirement Plan Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax				(284)
Adjusted balance beginning of period				(1,601)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,317)	(1,624)	(1,317)	(1,692)
OCI before reclassifications		(82)	(61)	(146)
Amounts reclassified from AOCI		34	38	521
OCI, net of tax		(48)	(23)	375
Ending balance		(1,672)	(1,624)	(1,317)
AOCI, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax		0		(5)			$ 0
Adjusted balance beginning of period			(1,579)	658			$ (337)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	663	(1,579)	663	(337)
OCI before reclassifications		1,742	(2,306)	731
Amounts reclassified from AOCI		(111)	69	269
OCI, net of tax		1,631	(2,237)	1,000
Ending balance		$ 52	$ (1,579)	663
Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Disposal Group, Including Discontinued Operations, Adjustments to AOCI				$ 1,000	$ 758	$ 758
Equity securities and shadow DAC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of accounting changes, net of tax	$ 93