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, 2018	Mar. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		237	276
Recognized from accumulated other comprehensive loss	[1]	130	151
Recognized from regulatory asset		88	106
Total recognized in net periodic benefit cost		218	257
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		88	107
Recognized from accumulated other comprehensive loss	[1]	88	107
Total recognized in net periodic benefit cost		88	107
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)		109	131
Recognized from accumulated other comprehensive loss	[1]	21	25
Recognized from regulatory asset		88	106
Total recognized in net periodic benefit cost		109	131
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		25	22
Recognized from accumulated other comprehensive loss	[1]	25	22
Total recognized in net periodic benefit cost		25	22
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)		15	16
Recognized from accumulated other comprehensive loss	[1]	(4)	(3)
Total recognized in net periodic benefit cost		$ (4)	$ (3)

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