Premises and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Premises and equipment
Total	$ 843,960,000	$ 819,265,000
Less accumulated depreciation	(324,763,000)	(298,630,000)
Net premises and equipment	519,197,000	520,635,000
Depreciation expense charged to operations	28,200,000	29,400,000	$ 29,200,000
2018-15
Premises and equipment
Capitalized implementation costs related to internal use software	0
Land
Premises and equipment
Total	132,717,000	133,105,000
Buildings and leasehold improvements
Premises and equipment
Total	$ 401,989,000	395,360,000
Buildings and leasehold improvements | Minimum
Premises and equipment
Useful Life	15 years
Buildings and leasehold improvements | Maximum
Premises and equipment
Useful Life	40 years
Equipment and furnishings
Premises and equipment
Total	$ 201,153,000	178,676,000
Equipment and furnishings | Minimum
Premises and equipment
Useful Life	3 years
Equipment and furnishings | Maximum
Premises and equipment
Useful Life	10 years
Lease right of use assets
Premises and equipment
Total	$ 100,331,000	107,979,000
Construction in process
Premises and equipment
Total	$ 7,770,000	4,145,000
Computer software
Premises and equipment
Useful Life	36 months
Total	$ 24,600,000	23,200,000
Unamortized balance remaining	4,300,000	7,800,000
Depreciation expense charged to operations	$ 4,900,000	$ 4,900,000	$ 4,800,000