Equity (Components of Other Comprehensive Income) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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		$ 113	$ (148)	$ 75
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax		(10)	(1)	25
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax		103	(149)	100
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap, Before Reclassification and Tax		(33)	87	(48)
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap Tax		7	(18)	17
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap Net Of Tax		(26)	69	(31)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax		80	(61)	27
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax		(3)	(19)	42
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		77	(80)	69
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax	[1]	3,208	(1,834)	1,030
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	[1]	(698)	394	(314)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	[1]	2,510	(1,440)	716
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax	[1]	84	(122)	25
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	[1]	(17)	26	(7)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	[1]	67	(96)	18
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments and Tax	[1]	3,124	(1,712)	1,005
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	[1]	(681)	368	(307)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	[1]	2,443	(1,344)	698
Other than Temporary Impairment Loss, Investments, Portion in Other Comprehensive Loss, before Tax, Portion Attributable to Parent, Available-for-sale Securities		0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Tax, Portion Attributable to Parent, Available-for-sale Securities		0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Net of Tax, Portion Attributable to Parent, Available-for-sale Securities		0	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(1)	(1)	12
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax		0	0	(4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax		(1)	(1)	8
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(23)	1	(11)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax		5	0	4
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		(18)	1	(7)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		(24)	0	1
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		5	0	0
Defined benefit pension and postretirement plan adjustments		(19)	0	1
Other Comprehensive Income (Loss), before Tax		3,180	(1,773)	1,033
Other Comprehensive Income (Loss), Tax		(679)	349	(265)
Other Comprehensive Income (Loss), Net of Tax		$ 2,501	$ (1,424)	$ 768

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