Borrowed Funds - Component of Short-Term and Long-Term Debt (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2023
Federal Home Loan Bank 5.04% due 2024 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	5.04%
Debt instrument, maturity year	2024
Federal Home Loan Bank 5.47% due 2023 [ Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	5.47%
Debt instrument, maturity year	2023
Federal Reserve Bank Term Funding Program 4.70% due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.70%
Debt instrument, maturity year	2023
Marquette Capital Trust I Subordinated Debentures 6.36% due 2036 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	6.36%
Debt instrument, maturity year	2036
Marquette Capital Trust II Subordinated Debentures 6.36% due 2036 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	6.36%
Debt instrument, maturity year	2036
Marquette Capital Trust III Subordinated Debentures 7.16% due 2036 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	7.16%
Debt instrument, maturity year	2036
Marquette Capital Trust IV Subordinated Debentures 7.27% due 2036
Debt Instrument [Line Items]
Debt instrument, interest rate	7.27%
Debt instrument, maturity year	2036
Subordinated notes 3.70% due 2030, net of issuance costs [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	3.70%
Debt instrument, maturity year	2030
Subordinated notes 6.25% due 2032, net issuance costs [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	6.25%
Debt instrument, maturity year	2032