AOCI Rollforward (Details 2) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 629	$ 262
OCI before reclassifications	(273)	(563)
Amounts reclassified from AOCI	(39)	6
Total other comprehensive income (loss), net of tax	(312)	(557)
Ending balance	317	(295)
Net unrealized gains (losses) on securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	983	576
OCI before reclassifications	(301)	(530)
Amounts reclassified from AOCI	(39)	6
Total other comprehensive income (loss), net of tax	(340)	(524)
Ending balance	643	52
Net unrealized gains (losses) on derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	5	6
OCI before reclassifications	0	0
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	0	0
Ending balance	5	6
Defined benefit plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(204)	(138)
OCI before reclassifications	29	0
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	29	0
Ending balance	(175)	(138)
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(154)	(181)
OCI before reclassifications	(1)	(33)
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss), net of tax	(1)	(33)
Ending balance	(155)	(214)
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
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)