Fair Value Disclosures - Financial Assets and Liabilities Not Recorded at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financial assets:
HTM securities	$ 19,886	$ 20,047
Loans and leases HFI, net of ALLL	147,496	147,455
Financial liabilities:
Time deposits	14,978	16,577
Long-term debt	24,729	23,709
Carrying Amount
Financial assets:
HTM securities	20,095	20,552
Loans and leases HFI, net of ALLL	147,496	147,455
Financial liabilities:
Time deposits	14,978	16,577
Long-term debt	24,729	23,709
Fair Value | Level 2
Financial assets:
HTM securities	19,886	20,047
Financial liabilities:
Time deposits	15,026	16,617
Long-term debt	24,977	23,723
Fair Value | Level 3
Financial assets:
Loans and leases HFI, net of ALLL	$ 146,077	$ 145,591