Shareholder's Equity - Changes in AOCI Components (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Changes in balances of each component of AOCI, net of tax
Beginning balance		$ 5,867	$ 5,729	$ 5,588
Total other comprehensive income (loss), net of tax		(626)	367	553
Ending balance		5,685	5,867	5,729
Total AOCI
Changes in balances of each component of AOCI, net of tax
Beginning balance		629	262	(291)
OCI before reclassifications		(199)	377	540
Amounts reclassified from AOCI		(427)	(10)	13
Total other comprehensive income (loss), net of tax		(626)	367	553
Ending balance		3	629	262
Net Unrealized Gains (Losses) on Securities
Changes in balances of each component of AOCI, net of tax
Beginning balance	[1]	983	576	20
OCI before reclassifications		(222)	416	551
Amounts reclassified from AOCI		(443)	(9)	5
Total other comprehensive income (loss), net of tax		(665)	407	556
Ending balance	[1]	318	983	576
Noncredit related impairments
Changes in balances of each component of AOCI, net of tax
Beginning balance		0	1
Ending balance		0	0	1
Net Unrealized Gains (Losses) on Derivatives
Changes in balances of each component of AOCI, net of tax
Beginning balance		5	6	8
Amounts reclassified from AOCI		(1)	(1)	(2)
Total other comprehensive income (loss), net of tax		(1)	(1)	(2)
Ending balance		4	5	6
Defined Benefit Plans
Changes in balances of each component of AOCI, net of tax
Beginning balance		(204)	(138)	(120)
OCI before reclassifications		36	(66)	(28)
Amounts reclassified from AOCI		17		10
Total other comprehensive income (loss), net of tax		53	(66)	(18)
Ending balance		(151)	(204)	(138)
Foreign Currency Translation
Changes in balances of each component of AOCI, net of tax
Beginning balance		(154)	(181)	(198)
OCI before reclassifications		(13)	27	17
Total other comprehensive income (loss), net of tax		(13)	27	17
Ending balance		(167)	(154)	(181)
Other
Changes in balances of each component of AOCI, net of tax
Beginning balance		(1)	(1)	(1)
Total other comprehensive income (loss), net of tax		0	0	0
Ending balance		$ (1)	$ (1)	$ (1)

[1] Includes nil, nil and $1 million of noncredit related impairments on securities and net unrealized gains (losses) on previously impaired securities as of December 31, 2021, 2020 and 2019, respectively.