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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (19)	$ (58)	$ (58)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		208	277	680	826
Recognized from accumulated other comprehensive loss	[1]	119	152	377	451
Recognized from regulatory asset		70	106	245	317
Total recognized in net periodic benefit cost		189	258	622	768
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		82	107	258	319
Recognized from accumulated other comprehensive loss	[1]	82	107	258	319
Total recognized in net periodic benefit cost		82	107	258	319
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)		86	131	302	392
Recognized from accumulated other comprehensive loss	[1]	16	25	57	75
Recognized from regulatory asset		70	106	245	317
Total recognized in net periodic benefit cost		86	131	302	392
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		25	22	75	65
Recognized from accumulated other comprehensive loss	[1]	25	22	75	65
Total recognized in net periodic benefit cost		25	22	75	65
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(19)	(58)	(58)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		15	17	45	50
Recognized from accumulated other comprehensive loss	[1]	(4)	(2)	(13)	(8)
Total recognized in net periodic benefit cost		$ (4)	$ (2)	$ (13)	$ (8)

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