Loans and the Allowance for Credit Losses - Additional Information (Detail)				3 Months Ended	9 Months Ended	12 Months Ended
	Nov. 22, 2019 USD ($)	Aug. 20, 2018 USD ($)	Apr. 05, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Contract	Dec. 31, 2018 USD ($) Contract
Financing Receivable, Recorded Investment [Line Items]
Net Deferred loan (costs) and fees				$ 3,200,000	$ 3,200,000	$ 4,800,000	$ 3,200,000
Unaccreted discount on purchased loans from acquisitions				49,300,000	49,300,000	51,900,000	49,300,000
Aggregate amount of residential real estate, home equity and consumer loans classified as substandard				22,900,000	22,900,000	28,300,000	22,900,000
Internally assigned loan grades to residential real estate, home equity and consumer loans				3,900,000	3,900,000	5,100,000	3,900,000
Loans acquired with deteriorated credit quality				9,741,000	9,741,000	$ 14,513,000	$ 9,741,000
Number of restructured contracts greater than $0 million | Contract						0	0
Threshold for TDR				1,000,000.0	1,000,000.0	$ 1,000,000.0	$ 1,000,000.0
Accruing and non accrual TDR permitted interest-only payment period						3 months
Unfunded commitments to debtors for impaired loans				100,000	100,000	$ 3,300,000	100,000
Other real estate owned				7,173,000	7,173,000	4,062,000	7,173,000
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality				2,430,000	2,430,000	4,104,000	2,430,000
Other real estate owned				1,300,000	1,300,000	600,000	1,300,000
Foreclosure proceedings in process on residential real estate loans				6,000,000.0	6,000,000.0	8,100,000	6,000,000.0
Cost Recovery Method [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality, fair value	$ 4,000,000.0	$ 2,400,000	$ 700,000
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality				900,000	900,000	883,000	$ 900,000
Commercial and Industrial [Member] | Maximum [Member]
Financing Receivable, Recorded Investment [Line Items]
Annual sales of borrowers						100,000,000
Farmers Capital Bank Corporation [Member]
Financing Receivable, Recorded Investment [Line Items]
Unaccreted discount on purchased loans from acquisitions						15,300,000
Portfolio loans, net of unearned income		1,064,800,000
Preliminary fair value of acquired loans		1,025,800,000
Fair market value adjustment of acquired loans		988,300,000
Fair market value adjustment of acquired loans		26,000,000.0
Loans acquired with deteriorated credit quality		5,300,000				2,800,000
Loans acquired with deteriorated credit quality, fair value		$ 4,600,000
Loans acquired with deteriorated credit quality outstanding customer balance						3,300,000
Acquired impaired loans allowances for loan losses						0
Acquired loans, sold book value				45,200,000
Acquired loans, sold				$ 32,900,000
Old Line Bancshares, Inc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Unaccreted discount on purchased loans from acquisitions						24,000,000.0
Portfolio loans, net of unearned income	2,570,000,000.0
Preliminary fair value of acquired loans	2,545,593,000
Fair market value adjustment of acquired loans	2,535,200,000
Fair market value adjustment of acquired loans	24,100,000
Loans acquired with deteriorated credit quality	10,700,000					10,100,000
Loans acquired with deteriorated credit quality, fair value	$ 10,400,000
Loans acquired with deteriorated credit quality outstanding customer balance						10,500,000
Acquired impaired loans allowances for loan losses						0
First Sentry Bancshares, Inc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Unaccreted discount on purchased loans from acquisitions						4,600,000
Portfolio loans, net of unearned income			465,900,000
Preliminary fair value of acquired loans			447,279,000
Fair market value adjustment of acquired loans			429,300,000
Fair market value adjustment of acquired loans			9,700,000
Loans acquired with deteriorated credit quality			5,100,000			500,000
Loans acquired with deteriorated credit quality, fair value			$ 2,300,000
Loans acquired with deteriorated credit quality outstanding customer balance						1,200,000
Acquired impaired loans allowances for loan losses						$ 0
Acquired loans, sold book value					21,700,000
Acquired loans, sold					$ 15,700,000