Shareholder's Equity - Changes in AOCI Components (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Changes in balances of each component of AOCI, net of tax
Beginning balance	$ 5,010	$ 5,502	$ 5,867	$ 5,685	$ 5,867
OCI before reclassifications	(912)	144		(1,794)	(129)
Amounts reclassified from AOCI	12	(1)		(4)	(40)
Total other comprehensive income (loss), net of tax	(900)	143		(1,798)	(169)
Ending balance	4,304	5,686	5,502	4,304	5,686
Total AOCI
Changes in balances of each component of AOCI, net of tax
Beginning balance	(895)	317	629	3	629
Total other comprehensive income (loss), net of tax	(900)	143		(1,798)	(169)
Ending balance	(1,795)	460	317	(1,795)	460
Net unrealized gains (losses) on securities
Changes in balances of each component of AOCI, net of tax
Beginning balance	(535)	643	983	318	983
OCI before reclassifications	(788)	142		(1,625)	(159)
Amounts reclassified from AOCI	12	(1)		(4)	(40)
Total other comprehensive income (loss), net of tax	(776)	141		(1,629)	(199)
Ending balance	(1,311)	784	643	(1,311)	784
Net unrealized gains (losses) on derivatives
Changes in balances of each component of AOCI, net of tax
Beginning balance	5	5	5	4	5
OCI before reclassifications	(2)	0		(1)	0
Amounts reclassified from AOCI	0	0		0	0
Total other comprehensive income (loss), net of tax	(2)	0		(1)	0
Ending balance	3	5	5	3	5
Defined benefit plans
Changes in balances of each component of AOCI, net of tax
Beginning balance	(151)	(175)	(204)	(151)	(204)
OCI before reclassifications	0	0		0	29
Amounts reclassified from AOCI	0	0		0	0
Total other comprehensive income (loss), net of tax	0	0		0	29
Ending balance	(151)	(175)	(175)	(151)	(175)
Foreign currency translation
Changes in balances of each component of AOCI, net of tax
Beginning balance	(213)	(155)	(154)	(167)	(154)
OCI before reclassifications	(122)	2		(168)	1
Amounts reclassified from AOCI	0	0		0	0
Total other comprehensive income (loss), net of tax	(122)	2		(168)	1
Ending balance	(335)	(153)	(155)	(335)	(153)
Other
Changes in balances of each component of AOCI, net of tax
Beginning balance	(1)	(1)	(1)	(1)	(1)
OCI before reclassifications	0	0		0	0
Amounts reclassified from AOCI	0	0		0	0
Total other comprehensive income (loss), net of tax	0	0		0	0
Ending balance	$ (1)	$ (1)	$ (1)	$ (1)	$ (1)