Investment Securities (Details Textual) - USD ($)	3 Months Ended						12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investment Securities Information [Line Items]
Interest receivable							$ 80,528,000	$ 90,263,000
Proceeds from sales of investment securities		$ 51,000,000					158,708,000	626,283,000	$ 1,367,476,000
Debt Securities, Held-to-maturity, transfer to AFS					$ 692,000,000
Investment Securities (Textuals) [Abstract]
Debt Securities AFS Principal Sold			$ 261,000,000	$ 281,000,000					157,000,000
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)			$ 3,000,000	$ 6,000,000
Transfer of HTM securities to AFS securities (adoption of ASU 2019-04)							$ 0	0	692,414,000
Debt Securities, Available-for-sale, Gain (Loss)									3,000,000
Carrying amount of Securities Sold									$ 1,200,000,000
Visa Restricted Stock Owned. Total							77,996
Visa Restricted Stock Owned at Fair Value [Member]						77,000	77,000
Visa Restricted Stock Donated [Member]						42,039
Pledged Financial Instruments, Not Separately Reported, Securities							$ 2,300,000,000	2,100,000,000
Interest receivable							80,528,000	90,263,000
Debt Securities, HTM, Past Due Status							0
Held to maturity allowance for credit loss							(55,000)	(67,000)
Federal Home Loan Bank Stock							82,000,000	82,000,000
Federal Reserve Bank Stock							87,000,000	87,000,000
Equity Securities with Readily Determined Fair Value							5,000,000	2,000,000
Equity Securities without Readily Determinable Fair Value, Amount							14,000,000	13,000,000
Visa Restricted Stock Owned at Zero Cost				996
Debt Securities, Held-to-maturity, Transfer [Abstract]
Debt Securities, Held-to-maturity, transfer to AFS					692,000,000
Gain (Loss) on Securities [Line Items]
Debt Securities, Held-to-maturity, transfer to AFS					$ 692,000,000
First Staunton Bancshares
Investment Securities Information [Line Items]
Carrying amount of Securities Sold				$ 84,000,000
Investment Securities (Textuals) [Abstract]
Carrying amount of Securities Sold				$ 84,000,000
Held-to-maturity Securities
Investment Securities Information [Line Items]
Interest receivable							15,000,000	14,000,000
Investment Securities (Textuals) [Abstract]
Interest receivable							15,000,000	14,000,000
Available-for-sale Securities [Member]
Investment Securities Information [Line Items]
Interest receivable							9,000,000	8,000,000
Investment Securities (Textuals) [Abstract]
Interest receivable							9,000,000	8,000,000
Federal Home Loan Bank Certificates and Obligations (FHLB) [Member]
Investment Securities Information [Line Items]
Interest receivable							975,000	972,000
Investment Securities (Textuals) [Abstract]
Interest receivable							975,000	972,000
Federal Reserve Bank Stock [Member]
Investment Securities Information [Line Items]
Interest receivable							0	0
Investment Securities (Textuals) [Abstract]
Interest receivable							$ 0	$ 0
FFELP asset backed securities
Investment Securities Information [Line Items]
Proceeds from Sale of Debt Securities, Available-for-sale	$ 107,000,000