Financial Derivatives (Total Derivatives) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Notional Amount	$ 441,494,000,000	$ 418,625,000,000
Derivative Asset, Fair Value	1,903,000,000	2,874,000,000
Derivative Liability, Fair Value	2,942,000,000	2,856,000,000
Derivative Asset, Fair Value Offset Amount	795,000,000	1,054,000,000
Derivative Liability Setoff Right Amount	795,000,000	1,054,000,000
Derivative Asset, Cash Collateral	45,000,000	636,000,000
Derivative Asset, Net Fair Value	1,063,000,000	1,184,000,000
Derivative Liability, Net Fair Value	1,499,000,000	1,039,000,000
Derivative Liability, Cash Collateral	648,000,000	763,000,000
Increase (Decrease) in Derivative Assets	(1,300,000,000)
Increase (Decrease) in Derivative Liabilities	(500,000,000)
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Notional Amount	59,569,000,000	58,994,000,000
Derivative Asset, Fair Value	129,000,000	174,000,000
Derivative Liability, Fair Value	165,000,000	111,000,000
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	32,810,000,000	34,059,000,000
Derivative Asset, Fair Value	75,000,000	114,000,000
Derivative Liability, Fair Value	105,000,000	94,000,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	25,647,000,000	23,875,000,000
Derivative Asset, Fair Value	54,000,000	60,000,000
Derivative Liability, Fair Value	9,000,000	6,000,000
Designated as Hedging Instrument [Member] | Net Investment Hedging [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,112,000,000	1,060,000,000
Derivative Asset, Fair Value
Derivative Liability, Fair Value	51,000,000	11,000,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Notional Amount	381,925,000,000	359,631,000,000
Derivative Asset, Fair Value	1,774,000,000	2,700,000,000
Derivative Liability, Fair Value	2,777,000,000	2,745,000,000
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	120,299,000,000	107,358,000,000
Derivative Asset, Fair Value	45,000,000	192,000,000
Derivative Liability, Fair Value	25,000,000	53,000,000
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Swap [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	54,578,000,000	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 [Member] | Mortgage Banking [Member] | Future [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	52,555,000,000	47,494,000,000
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Mortgage Commitment [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	6,796,000,000	8,999,000,000
Derivative Asset, Fair Value	30,000,000	19,000,000
Derivative Liability, Fair Value	18,000,000	9,000,000
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Other Contract [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	6,370,000,000	2,530,000,000
Derivative Asset, Fair Value	15,000,000	11,000,000
Derivative Liability, Fair Value	3,000,000	2,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	254,484,000,000	244,828,000,000
Derivative Asset, Fair Value	1,709,000,000	2,505,000,000
Derivative Liability, Fair Value	2,307,000,000	2,142,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	224,441,000,000	217,498,000,000
Derivative Asset, Fair Value	1,258,000,000	2,156,000,000
Derivative Liability, Fair Value	1,875,000,000	1,810,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	30,043,000,000	27,330,000,000
Derivative Asset, Fair Value	451,000,000	349,000,000
Derivative Liability, Fair Value	432,000,000	332,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Swap [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	200,489,000,000	194,042,000,000
Derivative Asset, Fair Value	1,182,000,000	2,079,000,000
Derivative Liability, Fair Value	1,807,000,000	1,772,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Future [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	3,274,000,000	3,453,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Mortgage Commitment [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	1,894,000,000	2,228,000,000
Derivative Asset, Fair Value	6,000,000	2,000,000
Derivative Liability, Fair Value	4,000,000	2,000,000
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Other Contract [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	18,784,000,000	17,775,000,000
Derivative Asset, Fair Value	70,000,000	75,000,000
Derivative Liability, Fair Value	64,000,000	36,000,000
Not Designated as Hedging Instrument [Member] | Other Risk Management Activity [Member] | Foreign Exchange And Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	7,142,000,000	7,445,000,000
Derivative Asset, Fair Value	20,000,000	3,000,000
Derivative Liability, Fair Value	$ 445,000,000	$ 550,000,000