Loans and Allowance for Credit Losses, Commitments to Lend (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Temporary Advance Arrangements	$ 94,000	$ 91,000
Total unfunded credit commitments	573,978	558,701
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	353,115	353,876
Commercial and industrial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	329,751	330,492
Commercial real estate mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	7,905	6,984
Commercial real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	15,459	16,400
Total Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	220,863	204,825
Real estate 1-4 family first mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	43,427	29,736
Real estate 1-4 family junior lien mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	37,454	37,719
Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	113,306	109,840
Other revolving credit and installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	26,676	27,530
International [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial Letters of Credit International	$ 1,000	$ 919