Other Comprehensive Income (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended				6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Balance at beginning of period		$ 65,474	$ 64,170	$ 60,006	$ 58,543	$ 64,170	$ 58,543
Other comprehensive income (loss) before reclassifications, net of tax	$ (5)
Other comprehensive income (loss), net of tax		526	(332)	251	331	194	582
Balance at end of period	65,474	68,355	65,474	61,599	60,006	68,355	61,599
Net unrealized investment gains (losses)
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Balance at beginning of period		463	774	431	97	774	97
Other comprehensive income (loss) before reclassifications, net of tax		560		259		166	607
Amounts reclassified from accumulated other comprehensive loss, net of tax		(36)		(8)		47	(22)
Other comprehensive income (loss), net of tax		524		251		213	585
Balance at end of period	463	987	463	682	431	987	682
OCI before Reclass, pre-tax		681		309		195	719
Amounts reclassified, pre-tax		(44)		(11)		57	(30)
Foreign currency translation adjustments
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Balance at beginning of period		(8)	4	(157)	(158)	4	(158)
Other comprehensive income (loss) before reclassifications, net of tax		6		3		(6)	4
Other comprehensive income (loss), net of tax		6		3		(6)	4
Balance at end of period	(8)	(2)	(8)	(154)	(157)	(2)	(154)
Net cash flow hedges
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Balance at beginning of period		270	279	308	312	279	312
Other comprehensive income (loss) before reclassifications, net of tax		0		0		(5)	0
Amounts reclassified from accumulated other comprehensive loss, net of tax		(3)		(3)		(7)	(7)
Other comprehensive income (loss), net of tax		(3)		(3)		(12)	(7)
Balance at end of period	270	267	270	305	308	267	305
Amount expected to be reclassified		15				15
OCI before Reclass, pre-tax		0		0		(7)	0
Amounts reclassified, pre-tax		(4)		(4)		(10)	(9)
Pension and OPEB plans
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Balance at beginning of period		(38)	(38)	(149)	(149)	(38)	(149)
Other comprehensive income (loss) before reclassifications, net of tax		(6)		0		(6)	0
Amounts reclassified from accumulated other comprehensive loss, net of tax		5		0		5	0
Other comprehensive income (loss), net of tax		(1)		0		(1)	0
Balance at end of period	(38)	(39)	(38)	(149)	(149)	(39)	(149)
OCI before Reclass, pre-tax		(8)		0		(8)	0
Amounts reclassified, pre-tax		7		0		7	0
AOCI Including Portion Attributable to Noncontrolling Interest
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Balance at beginning of period		687	1,019	433	102	1,019	102
Balance at end of period	$ 687	$ 1,213	$ 687	$ 684	$ 433	$ 1,213	$ 684