Employee Benefit Plans - Amounts Included in Regulatory Asset and Accumulated Other Comprehensive Income/Loss Recognized as Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)	$ (57)	$ (57)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		230	217	690	651
Recognized from accumulated other comprehensive loss	[1]	87	89	260	267
Recognized from regulatory asset		124	109	373	327
Defined Benefit Plan Actuarial Gain Loss, Net Settlement			198		594
Total recognized in net periodic benefit cost		211	198	633	594
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		60	65	180	195
Recognized from accumulated other comprehensive loss	[1]	60	65	180	195
Total recognized in net periodic benefit cost		60	65	180	195
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		155	135	465	405
Recognized from accumulated other comprehensive loss	[1]	29	26	87	78
Recognized from regulatory asset		126	109	378	327
Total recognized in net periodic benefit cost		155	135	465	405
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		7	5	21	15
Recognized from accumulated other comprehensive loss	[1]	7	5	21	15
Defined Benefit Plan Actuarial Gain Loss, Net Settlement			5		15
Total recognized in net periodic benefit cost		7	5	21	15
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(19)	(57)	(57)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		10	12	30	36
Recognized from accumulated other comprehensive loss	[1]	(9)	(7)	(27)	(21)
Total recognized in net periodic benefit cost		(9)	$ (7)	(27)	$ (21)
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(2)		(6)
Recognized from accumulated other comprehensive loss	[1]			(1)
Recognized from regulatory asset		(2)		(5)
Total recognized in net periodic benefit cost		$ (2)		$ (6)

[1] See Note 9, Stockholders' Equity.