Premises and Equipment, Net of Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Premises and Equipment, Net of Accumulated Depreciation
Accumulated depreciation	$ (148,373)	$ (137,237)
Net premises and equipment, excluding ROU assets	263,236	241,528
ROU assets	47,073	0
Net premises and equipment	310,309	241,528
Land
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	52,738	47,511
Buildings and construction in progress
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	251,151	231,854
Furniture, fixtures and equipment
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	96,576	90,030
Leasehold improvements
Premises and Equipment, Net of Accumulated Depreciation
Premises and equipment, gross	$ 11,144	$ 9,370