Other Assets Other Assests (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	[5]	Jun. 30, 2018		Jun. 30, 2017	[7]	Dec. 31, 2017
Reclassification of Equity Securities from Nommarketable to Marketable						$ 22
Mutual Fund Investments	[1]	$ 95				95				$ 49
Marketable Securities, Equity Securities	[1],[2]	31				31				7
Securities Owned Not Readily Marketable	[2]	42				42				26
Federal Home Loan Bank Stock	[1]	90				90				15
Federal Reserve Bank Stock	[1]	403				403				403
Net Investment in Lease		1,705				1,705				1,528
Bank Owned Life Insurance		1,409				1,409				1,411
Accrued Investment Income Receivable		995				995				880
Receivables from Customers		860				860				2,201
Defined Benefit Plan, Funded (Unfunded) Status of Plan		497				497				464
Prepaid Expense		257				257				319
Other Real Estate		53				53				57
Other Assets, Miscellaneous		921				921				786
Other Assets	[3]	8,792				8,792				9,418
Gain (Loss) on Sale of Securities, Net		0	[4]	$ 1		1	[6]	$ 1
Marketable Equity Securities [Member]
Unrealized Gain (Loss) on Securities	[8]	13				14
Nonmarketable Equity Securities [Member]
Unrealized Loss on Securities		0				0
Unrealized Gain on Securities	[8]	0				23
Equity Securities [Member]
Unrealized Gain (Loss) on Securities		13				37
Gain (Loss) on Sale of Securities, Net		0				0
Tax Credit Investments [Member]
Other Assets	[9]	$ 1,434				$ 1,434				$ 1,272

[1] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets on the Consolidated Balance Sheets. Reclassifications have been made to previously reported amounts for comparability.

[2] During the second quarter of 2018, the Company reclassified $22 million of equity securities from nonmarketable to marketable equity securities due to newly available, readily determinable fair value information observed in active markets.

[3] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets. Reclassifications have been made to previously reported amounts for comparability.

[4] Amounts are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers, except for out of scope amounts.

[5] Amounts for periods prior to January 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition, and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers.

[6] Amounts are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers, except for out of scope amounts.

[7] Amounts for periods prior to January 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition, and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers.

[8] Recognized in Other noninterest income in the Company's Consolidated Statements of Income.

[9] See Note 10, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.