Premises and Equipment, Summary Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 786,761
Accumulated Depreciation	367,847
Net Book Value	418,914	$ 435,284
Land
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	70,431
Accumulated Depreciation	0
Net Book Value	70,431	69,649
Land improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	18,488
Accumulated Depreciation	8,716
Net Book Value	9,771	9,355
Buildings and improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	390,298
Accumulated Depreciation	168,136
Net Book Value	222,162	230,358
Computers
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	52,846
Accumulated Depreciation	38,128
Net Book Value	14,718	13,242
Furniture, fixtures and other equipment
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	174,362
Accumulated Depreciation	116,304
Net Book Value	58,058	53,342
Operating leases
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	46,632
Accumulated Depreciation	14,638
Net Book Value	31,994	45,381
Leasehold improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	33,706
Accumulated Depreciation	21,925
Net Book Value	$ 11,781	$ 13,958