Employee Benefit Plans (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost		$ (19)	$ (19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(237)	(276)
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		10	10
Amortization of prior service cost		(19)	(19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(15)	(16)
Net periodic cost (benefit)	[1]	6	7
Total periodic cost		6	7
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		12	13
Net periodic cost (benefit)	[1]	12	13
Amortization of pre-merger regulatory asset		2	2
Total periodic cost		14	15
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		592	623
Expected return on plan assets		(774)	(699)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(109)	(131)
Net periodic cost (benefit)	[1]	(73)	55
Amortization of pre-merger regulatory asset		191	191
Total periodic cost		118	246
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		21	22
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(25)	(22)
Net periodic cost (benefit)	[1]	46	44
Total periodic cost		46	44
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		97	103
Expected return on plan assets		(138)	(127)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(88)	(107)
Net periodic cost (benefit)	[1]	47	83
Total periodic cost		$ 47	$ 83

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