Equity (Components of Other Comprehensive Income) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax		$ 43	$ 113	$ (148)
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax		3	(10)	(1)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax		46	103	(149)
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap, Before Reclassification and Tax		(29)	(33)	87
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap Tax		6	7	(18)
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap Net Of Tax		(23)	(26)	69
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax		14	80	(61)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax		9	(3)	(19)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		23	77	(80)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax	[1]	2,812	3,208	(1,834)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	[1]	(614)	(698)	394
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	[1]	2,198	2,510	(1,440)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax	[1]	(8)	84	(122)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	[1]	(1)	(17)	26
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	[1]	(9)	67	(96)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments and Tax	[1]	2,820	3,124	(1,712)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	[1]	(613)	(681)	368
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	[1]	2,207	2,443	(1,344)
Other than Temporary Impairment Loss, Investments, Portion in Other Comprehensive Loss, before Tax, Portion Attributable to Parent, Available-for-sale Securities		(8)	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Tax, Portion Attributable to Parent, Available-for-sale Securities		2	0	0
Change in other-than-temporary impairment losses on fixed maturity securities		(6)	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(1)	(1)	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax		0	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax		(1)	(1)	(1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(2)	(23)	1
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax		1	5	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		(1)	(18)	1
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		(3)	(24)	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		1	5	0
Defined benefit pension and postretirement plan adjustments		(2)	(19)	0
Other Comprehensive Income (Loss), before Tax		2,823	3,180	(1,773)
Other Comprehensive Income (Loss), Tax		(601)	(679)	349
Other Comprehensive Income (Loss), Net of Tax		$ 2,222	$ 2,501	$ (1,424)

[1] Includes cash flow hedges. See Note 5 for additional information on cash flow hedges.