Employee Benefit Plans (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost		$ (19)	$ (20)	$ (39)	$ (39)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		236	276	473	551
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		9	11	19	21
Amortization of prior service cost		(19)	(20)	(39)	(39)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		15	17	30	32
Net periodic cost (benefit)	[1]	5	8	10	14
Total periodic cost		5	8	10	14
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		13	13	26	26
Net periodic cost (benefit)	[1]	13	13	26	26
Amortization of pre-merger regulatory asset		2	2	4	4
Total periodic cost		15	15	30	30
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		592	624	1,184	1,247
Expected return on plan assets		(774)	(700)	(1,549)	(1,399)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		108	131	217	262
Net periodic cost (benefit)	[1]	(74)	55	(148)	110
Amortization of pre-merger regulatory asset		191	191	381	381
Total periodic cost		117	246	233	491
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		21	22	42	44
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		25	22	50	44
Net periodic cost (benefit)	[1]	46	44	92	88
Total periodic cost		46	44	92	88
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		98	103	195	206
Expected return on plan assets		(138)	(127)	(276)	(254)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		88	106	176	213
Net periodic cost (benefit)	[1]	48	82	95	165
Total periodic cost		$ 48	$ 82	$ 95	$ 165

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