Borrowed Funds - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt	$ 269,595	$ 70,372
Marquette Capital Trust I Subordinated Debentures 1.57% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	17,553	17,195
Marquette Capital Trust II Subordinated Debentures 1.57% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	18,149	17,814
Marquette Capital Trust III Subordinated Debentures 1.74% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	7,139	7,008
Marquette Capital Trust IV Subordinated Debentures 1.82% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	28,873	$ 28,355
Subordinated notes 3.70% due 2030, net of issuance costs [Member]
Debt Instrument [Line Items]
Long-term debt	$ 197,881