Fair Value Disclosures - Financial Assets and Liabilities Not Recorded at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Financial assets:
HTM securities	$ 20,047	$ 22,837
Loans and leases HFI, net of ALLL	147,455	142,211
Financial liabilities:
Time deposits	16,577	13,170
Long-term debt	23,709	23,648
Carrying Amount
Financial assets:
HTM securities	20,552	23,027
Loans and leases HFI, net of ALLL	147,455	142,211
Financial liabilities:
Time deposits	16,577	13,170
Long-term debt	23,709	23,648
Fair Value | Level 2
Financial assets:
HTM securities	20,047	22,837
Financial liabilities:
Time deposits	16,617	13,266
Long-term debt	23,723	23,885
Fair Value | Level 3
Financial assets:
Loans and leases HFI, net of ALLL	$ 145,591	$ 141,664