Commitment, Changes in the Allowance for Unfunded Commitments (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Jan. 01, 2020
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 21,907
Allowance for Unfunded Commitments	57,276	$ 21,907
Provision for loan losses	16,500
Balance at end of period	57,276	21,907
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	21,907
Balance at end of period	57,276	21,907
Cumulative Effect, Period Of Adoption, Adjusted Balance
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Allowance for Unfunded Commitments			$ 40,597
First Staunton Bancshares [Member]
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Provision for loan losses	179
Accounting Standards Update 2016-13 | Cumulative Effect, Period Of Adoption, Adjustment
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Allowance for Unfunded Commitments			$ 18,690
SEC Schedule, 12-09, Reserve, Off-balance Sheet Activity [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	21,907	24,336
Balance at beginning of period, adjusted		24,336
Provision for unfunded commitments	$ 17,000	(2,500)
Balance at end of period		21,907
Amount Recorded at Acquisition [Member] | SEC Schedule, 12-09, Reserve, Off-balance Sheet Activity [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Amount recorded at acquisition		$ 70