Borrowed Funds - Components of Short-Term and Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Short-term debt	$ 1,800,000	$ 1,800,000
Long-term debt	383,742	383,247
Total borrowed funds	2,183,742	2,183,247
Federal Home Loan Bank 5.04% and 5.04% [Member]
Debt Instrument [Line Items]
Short-term debt	1,000,000	1,000,000
Federal Reserve Bank Term Funding Program 4.76% and 4.83% [Member]
Debt Instrument [Line Items]
Short-term debt	800,000	800,000
Marquette Capital Trust I Subordinated Debentures 6.91% [Member]
Debt Instrument [Line Items]
Long-term debt	18,682	18,607
Marquette Capital Trust II Subordinated Debentures 6.91% [Member]
Debt Instrument [Line Items]
Long-term debt	19,202	19,132
Marquette Capital Trust III Subordinated Debentures 7.08% [Member]
Debt Instrument [Line Items]
Long-term debt	7,544	7,517
Marquette Capital Trust IV Subordinated Debentures 7.19% [Member]
Debt Instrument [Line Items]
Long-term debt	30,460	30,356
Subordinated notes 3.70%, net of issuance costs [Member]
Debt Instrument [Line Items]
Long-term debt	199,344	199,232
Subordinated notes 6.25%, net issuance costs [Member]
Debt Instrument [Line Items]
Long-term debt	$ 108,510	$ 108,403