Goodwill and Other Intangible Assets (Aggregate Amortization Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	$ 19,916	$ 20,844	$ 22,050
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	16,864	17,132	18,566
Credit Card and Trust Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	2,637	2,883	2,682
Merchant Processing Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	$ 415	$ 829	$ 802

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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