Shareholder's Equity - Changes in AOCI Components (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Changes in balances of each component of AOCI, net of tax
Beginning balance	$ 5,685	$ 5,867
OCI before reclassifications	(882)	(273)
Amounts reclassified from AOCI	(16)	(39)
Total other comprehensive income (loss), net of tax	(898)	(312)
Ending balance	5,010	5,502
Total AOCI
Changes in balances of each component of AOCI, net of tax
Beginning balance	3	629
Total other comprehensive income (loss), net of tax	(898)	(312)
Ending balance	(895)	317
Net unrealized gains (losses) on securities
Changes in balances of each component of AOCI, net of tax
Beginning balance	318	983
OCI before reclassifications	(837)	(301)
Amounts reclassified from AOCI	(16)	(39)
Total other comprehensive income (loss), net of tax	(853)	(340)
Ending balance	(535)	643
Net unrealized gains (losses) on derivatives
Changes in balances of each component of AOCI, net of tax
Beginning balance	4	5
OCI before reclassifications	1	0
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	1	0
Ending balance	5	5
Defined benefit plans
Changes in balances of each component of AOCI, net of tax
Beginning balance	(151)	(204)
OCI before reclassifications	0	29
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	0	29
Ending balance	(151)	(175)
Foreign currency translation
Changes in balances of each component of AOCI, net of tax
Beginning balance	(167)	(154)
OCI before reclassifications	(46)	(1)
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	(46)	(1)
Ending balance	(213)	(155)
Other
Changes in balances of each component of AOCI, net of tax
Beginning balance	(1)	(1)
OCI before reclassifications	0	0
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	0	0
Ending balance	$ (1)	$ (1)