Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($) office	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment office	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of primary segments | segment									3
Net Interest Income	$ 32,983	$ 28,548	$ 27,469	$ 25,610	$ 25,454	$ 24,917	$ 24,813	$ 24,725	$ 114,610	$ 99,909	$ 94,904
Net Gains on Sales of Loans									3,004	3,280	3,359
Net Gains on Securities									706	596	1,979
Trust and Investment Product Fees									6,680	5,272	4,644
Insurance Revenues									8,330	7,979	7,741
Noncash Items:
Provision for Loan Losses									2,070	1,750	1,200
Depreciation and Amortization									6,184	4,687	4,315
Income Tax Expense (Benefit)									9,528	11,534	13,946
Segment Profit (Loss)	10,980	$ 12,639	$ 11,097	$ 11,813	11,621	$ 9,660	$ 9,839	$ 9,556	46,529	40,676	35,184
Segment Assets	3,929,090				3,144,360				3,929,090	3,144,360	2,955,994
Other
Segment Reporting Information [Line Items]
Net Interest Income									(1,118)	(765)	(666)
Net Gains on Sales of Loans									0	0	0
Net Gains on Securities									0	3	0
Trust and Investment Product Fees									0	(3)	(15)
Insurance Revenues									0	0	0
Noncash Items:
Provision for Loan Losses									0	0	0
Depreciation and Amortization									256	256	238
Income Tax Expense (Benefit)									(1,020)	(1,385)	(1,269)
Segment Profit (Loss)									(2,121)	21	(1,260)
Segment Assets	$ (11,178)				(9,801)				$ (11,178)	(9,801)	(12,936)
Core Banking
Segment Reporting Information [Line Items]
Number of banking offices | office	65								65
Core Banking | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income									$ 115,710	100,659	95,562
Net Gains on Sales of Loans									3,004	3,280	3,359
Net Gains on Securities									706	593	1,979
Trust and Investment Product Fees									4	3	(3)
Insurance Revenues									17	28	23
Noncash Items:
Provision for Loan Losses									2,070	1,750	1,200
Depreciation and Amortization									5,847	4,351	4,002
Income Tax Expense (Benefit)									9,671	12,262	14,306
Segment Profit (Loss)									46,075	39,520	35,070
Segment Assets	$ 3,926,242				3,142,096				3,926,242	3,142,096	2,958,585
Trust and Investment Advisory Services | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income									5	6	1
Net Gains on Sales of Loans									0	0	0
Net Gains on Securities									0	0	0
Trust and Investment Product Fees									6,676	5,272	4,662
Insurance Revenues									40	34	29
Noncash Items:
Provision for Loan Losses									0	0	0
Depreciation and Amortization									5	4	3
Income Tax Expense (Benefit)									437	145	168
Segment Profit (Loss)									1,263	217	227
Segment Assets	2,658				1,987				2,658	1,987	1,851
Insurance | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income									13	9	7
Net Gains on Sales of Loans									0	0	0
Net Gains on Securities									0	0	0
Trust and Investment Product Fees									0	0	0
Insurance Revenues									8,273	7,917	7,689
Noncash Items:
Provision for Loan Losses									0	0	0
Depreciation and Amortization									76	76	72
Income Tax Expense (Benefit)									440	512	741
Segment Profit (Loss)									1,312	918	1,147
Segment Assets	$ 11,368				$ 10,078				$ 11,368	$ 10,078	$ 8,494