Financial Derivatives (Total Derivatives) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Notional Amount	$ 460,873,000,000	$ 418,625,000,000
Derivative Asset, Fair Value	1,789,000,000	2,874,000,000
Derivative Liability, Fair Value	2,942,000,000	2,856,000,000
Derivative Asset, Fair Value Offset Amount	710,000,000	1,054,000,000
Derivative Liability, Fair Value Offset Amount	710,000,000	1,054,000,000
Derivative Asset, Cash Collateral	80,000,000	636,000,000
Derivative Asset, Net Fair Value	999,000,000	1,184,000,000
Derivative Liability, Cash Collateral	728,000,000	763,000,000
Derivative Liability, Net Fair Value	1,504,000,000	1,039,000,000
Increase (Decrease) in Derivative Assets	(1,800,000,000)
Increase (Decrease) in Derivative Liabilities	(600,000,000)
Designated as Hedging Instruments under GAAP [Member]
Derivative [Line Items]
Derivative Notional Amount	51,668,000,000	58,994,000,000
Derivative Asset, Fair Value	50,000,000	174,000,000
Derivative Liability, Fair Value		111,000,000
Designated as Hedging Instruments under GAAP [Member] | Fair Value Hedging [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	33,232,000,000	34,059,000,000
Derivative Asset, Fair Value	14,000,000	114,000,000
Derivative Liability, Fair Value		94,000,000
Designated as Hedging Instruments under GAAP [Member] | Cash Flow Hedging [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	17,394,000,000	23,875,000,000
Derivative Asset, Fair Value		60,000,000
Derivative Liability, Fair Value		6,000,000
Designated as Hedging Instruments under GAAP [Member] | Net Investment Hedging [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,042,000,000	1,060,000,000
Derivative Asset, Fair Value	36,000,000
Derivative Liability, Fair Value		11,000,000
Not Designated as Hedging Instrument under GAAP [Member]
Derivative [Line Items]
Derivative Notional Amount	409,205,000,000	359,631,000,000
Derivative Asset, Fair Value	1,739,000,000	2,700,000,000
Derivative Liability, Fair Value	2,942,000,000	2,745,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Mortgage Banking [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	126,522,000,000	107,358,000,000
Derivative Asset, Fair Value	26,000,000	192,000,000
Derivative Liability, Fair Value	21,000,000	53,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Mortgage Banking [Member] | Swap [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	71,254,000,000	48,335,000,000
Derivative Asset, Fair Value		162,000,000
Derivative Liability, Fair Value	3,000,000	42,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Mortgage Banking [Member] | Future [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	44,063,000,000	47,494,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Mortgage Banking [Member] | Mortgage Commitment [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	6,595,000,000	8,999,000,000
Derivative Asset, Fair Value	21,000,000	19,000,000
Derivative Liability, Fair Value	16,000,000	9,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Mortgage Banking [Member] | Other Contract [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	4,610,000,000	2,530,000,000
Derivative Asset, Fair Value	5,000,000	11,000,000
Derivative Liability, Fair Value	2,000,000	2,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	273,903,000,000	244,828,000,000
Derivative Asset, Fair Value	1,695,000,000	2,505,000,000
Derivative Liability, Fair Value	2,571,000,000	2,142,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	245,409,000,000	217,498,000,000
Derivative Asset, Fair Value	1,114,000,000	2,156,000,000
Derivative Liability, Fair Value	2,019,000,000	1,810,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member] | Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	28,494,000,000	27,330,000,000
Derivative Asset, Fair Value	581,000,000	349,000,000
Derivative Liability, Fair Value	552,000,000	332,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member] | Swap [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	216,998,000,000	194,042,000,000
Derivative Asset, Fair Value	1,039,000,000	2,079,000,000
Derivative Liability, Fair Value	1,946,000,000	1,772,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member] | Future [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	3,550,000,000	3,453,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member] | Mortgage Commitment [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	3,280,000,000	2,228,000,000
Derivative Asset, Fair Value	9,000,000	2,000,000
Derivative Liability, Fair Value	2,000,000	2,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member] | Other Contract [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	21,581,000,000	17,775,000,000
Derivative Asset, Fair Value	66,000,000	75,000,000
Derivative Liability, Fair Value	71,000,000	36,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Other Risk Management Activity [Member] | Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	8,780,000,000	7,445,000,000
Derivative Asset, Fair Value	18,000,000	3,000,000
Derivative Liability, Fair Value	$ 350,000,000	$ 550,000,000