Employee Benefit Plans - Summary of Benefit Obligations and Funded Status of the Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation at end of year	$ 142,980	$ 120,445
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	128,758	130,307
Service cost	2,248	2,835	$ 2,578
Interest cost	5,266	4,517	4,393
Actuarial loss (gain)	22,395	(12,458)
Acquisition		8,560
Benefits paid	(4,707)	(5,003)
Projected benefit obligation at end of year	153,960	128,758	130,307
Change in fair value of plan assets:
Fair value of plan assets at beginning of year	141,108	142,422
Actual return on plan assets	28,319	(5,587)
Employer contribution	3,000	2,500	5,000
Acquisition		6,776
Benefits paid	(4,707)	(5,003)
Fair value of plan assets at end of year	167,720	141,108	142,422
Amounts recognized in the statement of financial position:
Funded status	13,760	12,351
Net amounts recognized as receivable pension costs in the consolidated balance sheets	13,760	12,351
Amounts recognized in accumulated other comprehensive income consist of:
Unrecognized prior service cost	52	78
Unrecognized net loss	24,486	24,780
Net amounts recognized in accumulated other comprehensive income (before tax)	24,538	24,858
Unrecognized net loss (gain)	$ (24,486)	$ (24,780)
Weighted average assumptions used to determine benefit obligations:
Discount rate	3.38%	4.48%
Rate of compensation increase	3.53%	3.62%
Expected long-term return on assets	6.30%	6.30%
Farmers Capital Bank Corporation Postretirement Medical Benefit Plan [Member]
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 11,514	$ 9,518
Interest cost	460	138
Actuarial loss (gain)	1,304	(151)
Benefits paid	(1,038)	(199)
Projected benefit obligation at end of year	12,632	11,514	$ 9,518
Plan amendment		2,135
Participant contributions	392	73
Amounts recognized in the statement of financial position:
Funded status	12,632	11,514
Net amounts recognized as receivable pension costs in the consolidated balance sheets	(12,632)	(11,514)
Amounts recognized in accumulated other comprehensive income consist of:
Unrecognized prior service cost	(3,016)	(3,240)
Unrecognized net loss	(1,153)	151
Net amounts recognized in accumulated other comprehensive income (before tax)	(1,863)	(3,391)
Unrecognized net loss (gain)	$ 1,153	$ (151)
Weighted average assumptions used to determine benefit obligations:
Discount rate	3.35%	4.09%