Financial Derivatives (Total Derivatives) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Notional Amount	$ 474,664,000,000	$ 418,625,000,000
Derivative Asset, Fair Value	1,892,000,000	2,874,000,000
Derivative Liability, Fair Value	2,883,000,000	2,856,000,000
Derivative Asset, Fair Value Offset Amount	742,000,000	1,054,000,000
Derivative Liability, Fair Value Offset Amount	742,000,000	1,054,000,000
Derivative Asset, Cash Collateral	92,000,000	636,000,000
Derivative Asset, Net Fair Value	1,058,000,000	1,184,000,000
Derivative Liability, Cash Collateral	723,000,000	763,000,000
Derivative Liability, Net Fair Value	1,418,000,000	1,039,000,000
Increase (Decrease) in Derivative Assets	(1,700,000,000)
Increase (Decrease) in Derivative Liabilities	(500,000,000)
Designated as Hedging Instruments under GAAP [Member]
Derivative [Line Items]
Derivative Notional Amount	55,463,000,000	58,994,000,000
Derivative Asset, Fair Value	37,000,000	174,000,000
Derivative Liability, Fair Value	13,000,000	111,000,000
Designated as Hedging Instruments under GAAP [Member] | Fair Value Hedging [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	32,612,000,000	34,059,000,000
Derivative Asset, Fair Value	14,000,000	114,000,000
Derivative Liability, Fair Value	13,000,000	94,000,000
Designated as Hedging Instruments under GAAP [Member] | Cash Flow Hedging [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	21,802,000,000	23,875,000,000
Derivative Asset, Fair Value	4,000,000	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	1,049,000,000	1,060,000,000
Derivative Asset, Fair Value	19,000,000
Derivative Liability, Fair Value		11,000,000
Not Designated as Hedging Instrument under GAAP [Member]
Derivative [Line Items]
Derivative Notional Amount	419,201,000,000	359,631,000,000
Derivative Asset, Fair Value	1,855,000,000	2,700,000,000
Derivative Liability, Fair Value	2,870,000,000	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	135,968,000,000	107,358,000,000
Derivative Asset, Fair Value	43,000,000	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	69,325,000,000	48,335,000,000
Derivative Asset, Fair Value		162,000,000
Derivative Liability, Fair Value	4,000,000	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	53,525,000,000	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	6,808,000,000	8,999,000,000
Derivative Asset, Fair Value	30,000,000	19,000,000
Derivative Liability, Fair Value	17,000,000	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	6,310,000,000	2,530,000,000
Derivative Asset, Fair Value	13,000,000	11,000,000
Derivative Liability, Fair Value		2,000,000
Not Designated as Hedging Instrument under GAAP [Member] | Customer Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	274,802,000,000	244,828,000,000
Derivative Asset, Fair Value	1,748,000,000	2,505,000,000
Derivative Liability, Fair Value	2,461,000,000	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	245,577,000,000	217,498,000,000
Derivative Asset, Fair Value	1,216,000,000	2,156,000,000
Derivative Liability, Fair Value	1,944,000,000	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	29,225,000,000	27,330,000,000
Derivative Asset, Fair Value	532,000,000	349,000,000
Derivative Liability, Fair Value	517,000,000	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	218,121,000,000	194,042,000,000
Derivative Asset, Fair Value	1,140,000,000	2,079,000,000
Derivative Liability, Fair Value	1,875,000,000	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	3,801,000,000	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	2,582,000,000	2,228,000,000
Derivative Asset, Fair Value	7,000,000	2,000,000
Derivative Liability, Fair Value	4,000,000	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	21,073,000,000	17,775,000,000
Derivative Asset, Fair Value	69,000,000	75,000,000
Derivative Liability, Fair Value	65,000,000	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	8,431,000,000	7,445,000,000
Derivative Asset, Fair Value	64,000,000	3,000,000
Derivative Liability, Fair Value	$ 388,000,000	$ 550,000,000