Borrowed Funds - Component of Short-Term and Long-Term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Short-term debt	$ 2,300,000
Long-term debt	382,768	$ 381,311
Total borrowed funds	2,682,768	381,311
Federal Home Loan Bank 5.04% due 2024 [Member]
Debt Instrument [Line Items]
Short-term debt	1,000,000
Federal Home Loan Bank 5.47% due 2023 [ Member]
Debt Instrument [Line Items]
Short-term debt	500,000
Federal Reserve Bank Term Funding Program 4.70% due 2023 [Member]
Debt Instrument [Line Items]
Short-term debt	800,000
Marquette Capital Trust I Subordinated Debentures 6.36% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	18,538	18,319
Marquette Capital Trust II Subordinated Debentures 6.36% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	19,067	18,863
Marquette Capital Trust III Subordinated Debentures 7.16% due 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	7,492	7,415
Marquette Capital Trust IV Subordinated Debentures 7.27% due 2036
Debt Instrument [Line Items]
Long-term debt	30,256	29,956
Subordinated notes 3.70% due 2030, net of issuance costs [Member]
Debt Instrument [Line Items]
Long-term debt	199,118	198,781
Subordinated notes 6.25% due 2032, net issuance costs [Member]
Debt Instrument [Line Items]
Long-term debt	$ 108,297	$ 107,977