Fair Value of Financial Instruments (Fair Values of Financial Assets and Liabilities on Balance Sheets) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 499,682	$ 152,100		$ 161,251			$ 115,193
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	243,100	66,458
Debt Securities, Held-to-maturity, Fair Value	240,000	68,082
Loans held for sale	2,699	4,659
Cash Surrender Value, Fair Value Disclosure	72,920	71,591
Servicing Asset	2,294	2,486					$ 2,742
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Valuation Allowance for Impairment of Recognized Servicing Assets, Deductions for Aggregate Write-Downs	16	161
Commercial Portfolio Segment
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Financing Receivable, Allowance for Credit Loss	13,378	12,763	$ 8,686	$ 13,099	$ 10,106	$ 4,960
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	499,682	152,100
Debt Securities, Held-to-maturity, Fair Value	240,000	68,082
Other investment securities (b)	2,867	2,232
Loans and leases, net of deferred fees and costs	4,595,800	3,458,732
Cash Surrender Value, Fair Value Disclosure	72,920	71,591
Servicing Asset	2,300	2,600
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deposits, Fair Value Disclosure	5,546,935	3,773,602
Short-term Debt, Fair Value	186,028	74,170
Long-term Debt, Fair Value	106,497	117,364
Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	499,682	152,100
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	243,100	66,458
Federal Home Loan Bank ("FHLB") stock	17,918	21,718
Federal Reserve Bank ("FRB") stock	13,311	13,311
Other investment securities (b)	2,867	2,232
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deposits, Fair Value Disclosure	5,832,020	3,910,459
Short-term Debt, Fair Value	184,693	73,261
Long-term Debt, Fair Value	99,411	110,568
States and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	124,417	35,199
Debt Securities, Held-to-maturity, Fair Value	122,435	35,484
States and political subdivisions | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	124,181	35,139
States and political subdivisions | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	122,435	35,484
Residential mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	41,501	26,742
Residential mortgage-backed securities | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	41,501	26,742
Residential mortgage-backed securities | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	41,035	25,890
Commercial mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	46,917	5,856
Commercial mortgage-backed securities | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	46,917	5,856
Commercial mortgage-backed securities | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	47,889	5,429
Agency Securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	29,147
Agency Securities | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Held-to-maturity investment securities, at amortized cost (fair value of $240,000 at September 30, 2021 and $68,082 at December 31, 2020) (a)	29,995	0
Agency Securities | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	29,147	0
Nonqualified Plan [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Other investment securities (b)	2,083	1,867
Nonqualified Plan [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Other investment securities (b)	2,083	1,867
Other Security Investments [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Other investment securities (b)	$ 784	$ 365