Premises and Equipment (Major Classifications) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,261,459	$ 2,159,367
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,010,176	914,971
Property, Plant and Equipment, Net	1,251,283	1,244,396
Depreciation	108,641	103,828	$ 96,781
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	336,258	335,093
Premises and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,286,092	1,228,588
Furniture, equipment and software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 639,109	$ 595,686

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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