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, 2019	Mar. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		268	237
Recognized from accumulated other comprehensive loss	[1]	144	130
Recognized from regulatory asset		105	88
Total recognized in net periodic benefit cost		249	218
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		101	88
Recognized from accumulated other comprehensive loss	[1]	101	88
Total recognized in net periodic benefit cost		101	88
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)		129	109
Recognized from accumulated other comprehensive loss	[1]	24	21
Recognized from regulatory asset		105	88
Total recognized in net periodic benefit cost		129	109
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		26	25
Recognized from accumulated other comprehensive loss	[1]	26	25
Total recognized in net periodic benefit cost		26	25
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	15
Recognized from accumulated other comprehensive loss	[1]	(7)	(4)
Total recognized in net periodic benefit cost		$ (7)	$ (4)

[1] See Note 8, Stockholder's Equity.