Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Standby letters of credit and surety bonds		$ 33.0
Outstanding commitments to fund new loan and lease transactions		$ 940.7
Funding commitments for loans and leases expiration period		90 days
Other commitments due in 2024		$ 196.9
Other commitments due in 2025		108.8
Other commitments due in 2026		76.8
Other commitments due in 2027		74.7
Other commitments due in 2028		65.0
Other commitments due in 2028 and beyond		115.7
Environmental activities expenditures		$ 3.0	$ 4.6	$ 4.0
Environmental Remediation Expense, Statement of Income or Comprehensive Income [Extensible Enumeration]		Costs and Expenses	Costs and Expenses	Costs and Expenses
Non-recurring settlement charge, pre-tax	$ 600.0
Non-recurring settlement charge, after-tax	$ 446.4