Loans and Allowance for Loan Losses - Activity in ALL by Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				$ 51,389				$ 51,666	$ 51,389	$ 51,666
Charge- offs									(6,386)	(5,003)
Recoveries									948	924
Net charge- offs									(5,438)	(4,079)
Provisions charged to operations	$ 1,412	$ 2,758	$ 2,433	1,684	$ 1,516	$ 747	$ 1,225	314	8,287	3,802	$ 8,512
Balance at end of period	54,238				51,389				54,238	51,389	51,666
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				6,328				6,195	6,328	6,195
Charge- offs									(34)	(282)
Recoveries									25	17
Net charge- offs									(9)	(265)
Provisions charged to operations									721	398
Balance at end of period	7,040				6,328				7,040	6,328	6,195
Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				11,027				10,519	11,027	10,519
Charge- offs									(67)	(93)
Recoveries									42	41
Net charge- offs									(25)	(52)
Provisions charged to operations									155	560
Balance at end of period	11,157				11,027				11,157	11,027	10,519
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				3,261				3,226	3,261	3,226
Charge- offs									(146)	(174)
Recoveries									22	26
Net charge- offs									(124)	(148)
Provisions charged to operations									250	183
Balance at end of period	3,387				3,261				3,387	3,261	3,226
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				10,673				9,672	10,673	9,672
Charge- offs									(2,697)	(395)
Recoveries									30	106
Net charge- offs									(2,667)	(289)
Provisions charged to operations									2,143	1,290
Balance at end of period	10,149				10,673				10,149	10,673	9,672
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				13,151				15,334	13,151	15,334
Charge- offs									(514)	(2,257)
Recoveries									272	92
Net charge- offs									(242)	(2,165)
Provisions charged to operations									2,432	(18)
Balance at end of period	15,341				13,151				15,341	13,151	15,334
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				3,065				2,793	3,065	2,793
Charge- offs									(868)	(1,066)
Recoveries									218	245
Net charge- offs									(650)	(821)
Provisions charged to operations									904	1,093
Balance at end of period	3,319				3,065				3,319	3,065	2,793
Other Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				2,423				2,481	2,423	2,481
Charge- offs										(16)
Recoveries									90	361
Net charge- offs									90	345
Provisions charged to operations									119	(403)
Balance at end of period	2,632				2,423				2,632	2,423	2,481
Acquired Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period				$ 1,461				$ 1,446	1,461	1,446
Charge- offs									(2,060)	(720)
Recoveries									219	36
Net charge- offs									(1,841)	(684)
Provisions charged to operations									994	699
Balance at end of period	614				$ 1,461				614	$ 1,461	$ 1,446
Pegasus Bank [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Recoveries									30
Net charge- offs									30
Provisions charged to operations									569
Balance at end of period	$ 599								$ 599