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
		Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		217	268
Recognized from accumulated other comprehensive loss	[1]	89	144
Recognized from regulatory asset		109	105
Total recognized in net periodic benefit cost		198	249
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		65	101
Recognized from accumulated other comprehensive loss	[1]	65	101
Total recognized in net periodic benefit cost		65	101
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	129
Recognized from accumulated other comprehensive loss	[1]	26	24
Recognized from regulatory asset		109	105
Total recognized in net periodic benefit cost		135	129
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		5	26
Recognized from accumulated other comprehensive loss	[1]	5	26
Total recognized in net periodic benefit cost		5	26
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		12	12
Recognized from accumulated other comprehensive loss	[1]	(7)	(7)
Total recognized in net periodic benefit cost		$ (7)	$ (7)

[1] See Note 9, Stockholder's Equity.