Employee Benefit Plans (Detail) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2021		Sep. 30, 2020		Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost		$ (19)		$ (19)		$ (57)	$ (57)
Defined Benefit Plan Actuarial Gain Loss, Net Settlement				198			594
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		230		217		690	651
Defined Benefit Plan Amounts Recognized Gain (Loss)		211		198		633	594
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	87		89		260	267
Defined Benefit Plan Amounts Recognized From Regulatory Asset		124		109		373	327
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		200				300
Interest cost		34		46		102	138
Expected return on plan assets		(40)		(42)		(120)	(126)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		60		65		180	195
Net periodic cost (benefit)		54	[1]	69	[1]	162	207
Total periodic cost		54		69		162	207
Defined Benefit Plan Amounts Recognized Gain (Loss)		60		65		180	195
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	60		65		180	195
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		500				1,300
Interest cost		429		518		1,287	1,554
Expected return on plan assets		(830)		(745)		(2,490)	(2,235)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		155		135		465	405
Net periodic cost (benefit)		(246)	[1]	(92)	[1]	(738)	(276)
Amortization of pre-merger regulatory asset		0		0		0	0
Total periodic cost		(246)		(92)		(738)	(276)
Defined Benefit Plan Amounts Recognized Gain (Loss)		155		135		465	405
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	29		26		87	78
Defined Benefit Plan Amounts Recognized From Regulatory Asset		126		109		378	327
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		2,100				2,100
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		100
Interest cost		12		16		36	48
Defined Benefit Plan Actuarial Gain Loss, Net Settlement				5			15
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		7		5		21	15
Net periodic cost (benefit)		19	[1]	21	[1]	57	63
Total periodic cost		19		21		57	63
Defined Benefit Plan Amounts Recognized Gain (Loss)		7		5		21	15
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	7		5		21	15
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		200				200
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer						200
Interest cost		6		8		18	24
Amortization of prior service cost		(19)		(19)		(57)	(57)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		10		12		30	36
Net periodic cost (benefit)		(3)	[1]	1	[1]	(9)	3
Total periodic cost		(3)		1		(9)	3
Defined Benefit Plan Amounts Recognized Gain (Loss)		(9)		(7)		(27)	(21)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	(9)		(7)		(27)	(21)
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		200				200
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer						100
Interest cost		6		10		18	30
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(2)				(6)
Net periodic cost (benefit)		4	[1]	10	[1]	12	30
Amortization of pre-merger regulatory asset		0		2		0	6
Total periodic cost		4		$ 12		12	$ 36
Defined Benefit Plan Amounts Recognized Gain (Loss)		(2)				(6)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]					(1)
Defined Benefit Plan Amounts Recognized From Regulatory Asset		(2)				(5)
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		$ 100				$ 100

[1] See Note 9, Stockholders' Equity.