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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)	$ (57)	$ (58)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		217	257	651	683
Recognized from accumulated other comprehensive loss	[1]	89	24	267	312
Recognized from regulatory asset		109	104	327	313
Defined Benefit Plan Actuarial Gain Loss, Net Settlement			128
Total recognized in net periodic benefit cost		198	238	594	625
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		65	101	195	304
Recognized from accumulated other comprehensive loss	[1]	65	101	195	304
Total recognized in net periodic benefit cost		65	101	195	304
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)		135	128	405	386
Recognized from accumulated other comprehensive loss	[1]	26	24	78	73
Recognized from regulatory asset		109	104	327	313
Total recognized in net periodic benefit cost		135	128	405	386
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		5	17	15	(42)
Recognized from accumulated other comprehensive loss	[1]	5	(93)	15	(42)
Defined Benefit Plan Actuarial Gain Loss, Net Settlement			(93)		(68)
Total recognized in net periodic benefit cost		5	17	15	(42)
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(19)	(57)	(58)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		12	11	36	35
Recognized from accumulated other comprehensive loss	[1]	(7)	(8)	(21)	(23)
Total recognized in net periodic benefit cost		$ (7)	$ (8)	$ (21)	$ (23)

[1] See Note 9, Stockholders' Equity.