Commitment, Changes in the Allowance for Unfunded Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020		Dec. 31, 2019
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 21,907
Provision for loan losses	15,500
Balance at end of period	56,276		$ 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	56,276	[1]	21,907
First Staunton Bancshares [Member]
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Provision for loan losses	179
SEC Schedule, 12-09, Reserve, Off-balance Sheet Activity [Member]
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period, adjusted	40,597
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	16,000		(2,500)
Balance at end of period			21,907
SEC Schedule, 12-09, Reserve, Off-balance Sheet Activity [Member] | Accounting Standards Update 2016-13
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Cumulative effect of ASU 2016-13 adoption (CECL)	$ 18,690
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

[1] (b) At January 1, 2020, the adoption of ASU 2016-13 resulted in an increase to the allowance for loan losses of $112 million and an increase to the allowance for unfunded commitments of $19 million for a total increase to the ACLL of $131 million. A corresponding after tax decrease to common equity of $98 million was recorded along with a deferred tax asset of $33 million, included in accrued expenses and other liabilities. Prior periods were unadjusted due to the modified retrospective application of ASU 2016-13.