Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Standby letters of credit and surety bonds	$ 47.8
Outstanding commitments to fund new loan and lease transactions	$ 885.8
Funding commitments for loans and leases expiration period	90 days
Other commitments due in 2020	$ 119.8
Other commitments due in 2021	63.9
Other commitments due in 2022	60.6
Other commitments due in 2023	0.8
Other commitments due in 2024	0.0
Other commitments due in 2024 and beyond	0.0
Environmental activities expenditures	$ 1.3	$ 1.2	$ 1.9