Business Combinations - Consideration, Assets Acquired and Liabilities Assumed (Details) - USD ($)				9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Nov. 30, 2019	Sep. 30, 2020
Fair Value of Assets Acquired
Adjustments, Loans	$ (9,300,000)	$ (12,300,000)
Goodwill	373,417,000	371,621,000		$ 373,417,000
Fair Value of Liabilities Assumed
Goodwill	373,417,000	$ 371,621,000		373,417,000
As Recorded by DNB
Fair Value of Assets Acquired
Cash and cash equivalents			$ 64,119,000
Securities and other investments			108,715,000
Loans			917,127,000
Allowance for credit losses			(6,487,000)
Goodwill			15,525,000
Premises and equipment			6,782,000
Accrued interest receivable			4,138,000
Deferred income taxes			2,017,000
Core deposits and other intangible assets			269,000
Other assets			24,883,000
Total Assets Acquired			1,137,088,000
Fair Value of Liabilities Assumed
Deposits			966,263,000
Borrowings			37,617,000
Accrued interest payable and other liabilities			11,157,000
Total Liabilities Assumed			1,015,037,000
Total Net Assets Acquired			122,051,000
Identifiable Intangible Assets			269,000
Goodwill			15,525,000
DNB
Fair Value of Assets Acquired
Cash and cash equivalents	64,119,000		64,119,000	64,119,000
Adjustments, Cash and cash equivalents			0	0
Securities and other investments	108,898,000		108,898,000	108,898,000
Adjustments, Securities and other investments			183,000	0
Loans	906,607,000		908,984,000	906,607,000
Adjustments, Loans			(8,143,000)	(2,377,000)
Allowance for credit losses	0		0	0
Adjustments, Allowance for credit losses			6,487,000	0
Goodwill	85,970,000		84,175,000	85,970,000
Adjustments, Goodwill			(15,525,000)	1,795,000
Premises and equipment	14,872,000		14,872,000	14,872,000
Adjustments, Premises and equipment			8,090,000	0
Accrued interest receivable	4,138,000		4,138,000	4,138,000
Adjustments, Accrued interest receivable			0	0
Deferred income taxes	(970,000)		(1,281,000)	(970,000)
Adjustments, Deferred income taxes			(3,298,000)	311,000
Adjustments, Core deposits and other intangible assets			(269,000)
Other assets	20,497,000		20,605,000	20,497,000
Adjustments, Other assets			(4,278,000)	(108,000)
Total Assets Acquired	1,118,161,000		1,120,335,000	1,118,161,000
Adjustments, Total Assets Acquired			(16,753,000)	(2,174,000)
Fair Value of Liabilities Assumed
Deposits	967,265,000		967,265,000	967,265,000
Adjustments, Deposits			1,002,000	0
Borrowings	37,084,000		37,341,000	37,084,000
Adjustments, Borrowings			(276,000)	(257,000)
Accrued interest payable and other liabilities	7,851,000		7,973,000	7,851,000
Adjustments, Accrued interest payable and other liabilities			(3,184,000)	(122,000)
Total Liabilities Assumed	1,012,200,000		1,012,579,000	1,012,200,000
Adjustments, Total Liabilities Assumed			(2,458,000)	(379,000)
Total Net Assets Acquired	105,961,000		107,756,000	105,961,000
Adjustments, Total Net Assets Acquired			(14,295,000)	(1,795,000)
Total Fair Value of Net Assets Acquired and Identified	115,021,000		116,816,000	115,021,000
Adjustments, Total Fair Value of Net Assets Acquired and Identified				(1,795,000)
Cash	360,000		360,000
Common stock			200,631,000
Fair Value of Total Consideration	200,991,000		200,991,000
Goodwill	85,970,000		84,175,000	85,970,000
Core deposits | DNB
Fair Value of Assets Acquired
Core deposits and other intangible assets	7,288,000		7,288,000	7,288,000
Adjustments, Core deposits and other intangible assets				0
Fair Value of Liabilities Assumed
Identifiable Intangible Assets	7,288,000		7,288,000	7,288,000
Wealth management | DNB
Fair Value of Assets Acquired
Core deposits and other intangible assets	1,772,000		1,772,000	1,772,000
Adjustments, Core deposits and other intangible assets				0
Fair Value of Liabilities Assumed
Identifiable Intangible Assets	$ 1,772,000		$ 1,772,000	$ 1,772,000