Bank Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Bank premises and equipment
Less: accumulated depreciation	$ (526,939)	$ (498,641)
Bank premises and equipment, net	479,878	506,595
Building and Building Improvements [Member]
Bank premises and equipment
Bank premises and equipment, gross	$ 577,656	573,257
Building and Building Improvements [Member] \| Minimum [Member]
Bank premises and equipment
Estimated useful lives	5 years
Building and Building Improvements [Member] \| Maximum [Member]
Bank premises and equipment
Estimated useful lives	39 years
Furniture Equipment and Vehicles [Member]
Bank premises and equipment
Bank premises and equipment, gross	$ 311,313	313,880
Furniture Equipment and Vehicles [Member] \| Minimum [Member]
Bank premises and equipment
Estimated useful lives	1 year
Furniture Equipment and Vehicles [Member] \| Maximum [Member]
Bank premises and equipment
Estimated useful lives	20 years
Land [Member]
Bank premises and equipment
Bank premises and equipment, gross	$ 117,848	$ 118,099

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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-Name Accounting Standards Codification
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-Section 50
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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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