Business Combinations - Consideration, Assets Acquired and Liabilities Assumed (Details) - USD ($)		Nov. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Fair Value of Assets Acquired
Goodwill			$ 371,621,000	$ 287,446,000
Core deposits and other intangible assets			10,900,000
Fair Value of Liabilities Assumed
Identifiable Intangible Assets			10,900,000
Goodwill			371,621,000	$ 287,446,000
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 loan 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
Preliminary Fair Value Adjustments, Cash and cash equivalents	[1]	0
Securities and other investments		108,898,000
Preliminary Fair Value Adjustments, Securities and other investments	[1]	183,000
Loans		908,984,000	899,300,000
Preliminary Fair Value Adjustments, Loans	[1]	(8,143,000)
Allowance for loan losses		0
Preliminary Fair Value Adjustments, Allowance for loan losses	[1]	6,487,000
Goodwill		84,175,000	84,200,000
Preliminary Fair Value Adjustments, Goodwill	[1]	(15,525,000)
Premises and equipment		14,872,000
Preliminary Fair Value Adjustments, Premises and equipment	[1]	8,090,000
Accrued interest receivable		4,138,000
Preliminary Fair Value Adjustments, Accrued Interest Receivable	[1]	0
Deferred income taxes		(1,281,000)
Preliminary Fair Value Adjustments, Deferred income taxes	[1]	(3,298,000)
Preliminary Fair Value Adjustments, Core deposits and other intangible assets	[1]	(269,000)
Other assets		20,605,000
Preliminary Fair Value Adjustments, Other assets	[1]	(4,278,000)
Total Assets Acquired		1,120,335,000
Preliminary Fair Value Adjustments, Total Assets Acquired	[1]	(16,753,000)
Fair Value of Liabilities Assumed
Deposits		967,265,000
Preliminary Fair Value Adjustments, Deposits	[1]	1,002,000
Borrowings		37,341,000
Preliminary Fair Value Adjustments, Borrowings	[1]	(276,000)
Accrued interest payable and other liabilities		7,973,000
Preliminary Fair Value Adjustments, Accrued interest payable and other liabilities	[1]	(3,184,000)
Total Liabilities Assumed		1,012,579,000
Preliminary Fair Value Adjustments, Total Liabilities Assumed	[1]	(2,458,000)
Total Net Assets Acquired		107,756,000
Preliminary Fair Value Adjustments, Total Net Assets Acquired	[1]	(14,295,000)
Total Fair Value of Identifiable Net Assets		116,816,000
Cash		360,000
Common stock		200,631,000
Fair Value of Total Consideration		200,991,000
Goodwill		84,175,000	$ 84,200,000
Core Deposits | DNB
Fair Value of Assets Acquired
Core deposits and other intangible assets		7,288,000
Fair Value of Liabilities Assumed
Identifiable Intangible Assets		7,288,000
Wealth management | DNB
Fair Value of Assets Acquired
Core deposits and other intangible assets		1,772,000
Fair Value of Liabilities Assumed
Identifiable Intangible Assets		$ 1,772,000

[1] Management is continuing to evaluate the purchase accounting fair value adjustments related to loans, including loan classification, intangible assets, premises and equipment, deferred income taxes, other assets and borrowings until the final valuations and appraisals are complete. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.