Other Assets (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Mutual Fund Investments	[1],[2]	$ 65	$ 65	$ 49
Equity Securities, FV-NI	[1],[2],[3]	27	27	7
Federal Reserve Bank Stock	[1],[2]	403	403	403
Federal Home Loan Bank Stock	[1],[2]	142	142	15
Equity Securities without Readily Determinable Fair Value, Amount	[2],[3]	50	50	26
Net Investment in Lease		2,110	2,110	1,528
Bank Owned Life Insurance		1,619	1,619	1,411
Accrued Investment Income Receivable		1,059	1,059	880
Receivables from Customers		669	669	2,201
Defined Benefit Plan, Funded (Unfunded) Status of Plan		518	518	464
Prepaid Expense		248	248	319
Other Real Estate	[4]	52	52	57
Other Assets, Miscellaneous		887	887	786
Other Assets	[5]	9,432	9,432	9,418
Reclassification of Equity Securities from Nommarketable to Marketable			22
Equity Securities, FV-NI, Gain (Loss)	[6]	(4)	10
Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Annual Amount		0	0
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount	[6]	7	30
Equity Securities, FV-NI, Realized Gain (Loss)		0	0
Equity Securities [Member]
Unrealized Gain (Loss) on Securities		3	40
Tax Credit Investments [Member]
Other Assets	[7]	$ 1,583	$ 1,583	$ 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] Equity securities held for trading purposes are classified in Trading assets and derivative instruments or Trading liabilities and derivative instruments on the Company's Consolidated Balance Sheets.

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

[4] Does not include foreclosed real estate related to loans insured by the FHA or guaranteed by the VA. Proceeds due from the FHA and the VA are recorded as a receivable in Other assets in the Consolidated Balance Sheets until the property is conveyed and the funds are received. The receivable related to proceeds due from the FHA and the VA totaled $49 million and $45 million at September 30, 2018 and December 31, 2017, respectively.

[5] 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.

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

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