Employee Benefit Plans (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost		$ (19)	$ (19)	$ (58)	$ (58)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		208	277	680	826
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		10	11	29	31
Amortization of prior service cost		(19)	(19)	(58)	(58)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		15	17	45	50
Net periodic cost (benefit)	[1]	6	9	16	23
Total periodic cost		6	9	16	23
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		12	13	38	38
Net periodic cost (benefit)	[1]	12	13	38	38
Amortization of pre-merger regulatory asset		2	2	6	6
Total periodic cost		14	15	44	44
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		570	623	1,754	1,870
Expected return on plan assets		(770)	(699)	(2,318)	(2,098)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		86	131	302	392
Net periodic cost (benefit)	[1]	(114)	55	(262)	164
Amortization of pre-merger regulatory asset		191	191	571	571
Total periodic cost		77	246	309	735
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		21	22	63	66
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		25	22	75	65
Net periodic cost (benefit)	[1]	46	44	138	131
Total periodic cost		46	44	138	131
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		94	103	288	309
Expected return on plan assets		(131)	(127)	(406)	(381)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		82	107	258	319
Net periodic cost (benefit)	[1]	45	83	140	247
Total periodic cost		$ 45	$ 83	$ 140	$ 247

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