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		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)	$ (38)	$ (38)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		230	217	458	434
Recognized from accumulated other comprehensive loss	[1]	87	89	171	178
Recognized from regulatory asset		124	109	249	218
Defined Benefit Plan Actuarial Gain Loss, Net Settlement			198		396
Total recognized in net periodic benefit cost		211	198	420	396
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		60	65	120	130
Recognized from accumulated other comprehensive loss	[1]	60	65	120	130
Total recognized in net periodic benefit cost		60	65	120	130
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	310	270
Recognized from accumulated other comprehensive loss	[1]	29	26	58	52
Recognized from regulatory asset		126	109	252	218
Total recognized in net periodic benefit cost		155	135	310	270
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		7	5	14	10
Recognized from accumulated other comprehensive loss	[1]	7	5	14	10
Defined Benefit Plan Actuarial Gain Loss, Net Settlement			5		10
Total recognized in net periodic benefit cost		7	5	14	10
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(19)	(38)	(38)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		10	12	18	24
Recognized from accumulated other comprehensive loss	[1]	(9)	(7)	(20)	(14)
Total recognized in net periodic benefit cost		(9)	$ (7)	(20)	$ (14)
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)		(4)
Recognized from accumulated other comprehensive loss	[1]			(1)
Recognized from regulatory asset		(2)		(3)
Total recognized in net periodic benefit cost		$ (2)		$ (4)

[1] See Note 9, Stockholders' Equity.