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Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Jan. 01, 2020 USD ($) segment	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Number of segments | segment	3
Accrued interest receivable	$ 14,133,000
Required cash on deposit at Federal Reserve	0		$ 24,560,000
Net reduction to retained earnings upon adoption of new accounting pronouncement	(624,709,000)		(573,820,000)	$ (458,640,000)	$ (364,571,000)
Allowance for credit losses	46,859,000	$ 31,931,000	$ 16,278,000	15,823,000	15,694,000
Number of loan segments | segment		8	6
Acquired with Deteriorated Credit Quality
Property, Plant and Equipment [Line Items]
Allowance for credit losses			$ 405,000
Retained Earnings
Property, Plant and Equipment [Line Items]
Net reduction to retained earnings upon adoption of new accounting pronouncement	$ (288,447,000)		(253,090,000)	$ (211,424,000)	$ (178,969,000)
Cumulative Effect of Change in Accounting Principles
Property, Plant and Equipment [Line Items]
Net reduction to retained earnings upon adoption of new accounting pronouncement			6,717,000
Allowance for credit losses		$ 15,653,000
Cumulative Effect of Change in Accounting Principles | Acquired with Deteriorated Credit Quality
Property, Plant and Equipment [Line Items]
Allowance for credit losses		6,886,000	6,886,000
Cumulative Effect of Change in Accounting Principles | Retained Earnings
Property, Plant and Equipment [Line Items]
Net reduction to retained earnings upon adoption of new accounting pronouncement		$ 6,717,000	$ 6,717,000
Minimum
Property, Plant and Equipment [Line Items]
Finite-lived intangible asset, useful life	6 years
Maximum
Property, Plant and Equipment [Line Items]
Finite-lived intangible asset, useful life	10 years
Buildings and related components | Minimum
Property, Plant and Equipment [Line Items]
Premises, furniture, and equipment, useful life	10 years
Buildings and related components | Maximum
Property, Plant and Equipment [Line Items]
Premises, furniture, and equipment, useful life	40 years
Furniture, fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Premises, furniture, and equipment, useful life	3 years
Furniture, fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Premises, furniture, and equipment, useful life	10 years

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