Employee Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	$ (19)	$ (20)	$ (58)	$ (60)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(277)	(274)	(826)	(815)
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	103	105	309	315
Expected return on plan assets	(127)	(131)	(381)	(392)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(107)	(103)	(319)	(309)
Net periodic cost (benefit)	83	77	247	232
Total periodic cost	83	77	247	232
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	623	635	1,870	1,894
Expected return on plan assets	(699)	(625)	(2,098)	(2,027)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(131)	(133)	(392)	(389)
Net periodic cost (benefit)	55	143	164	256
Amortization of pre-merger regulatory asset	191	191	571	571
Total periodic cost	246	334	735	827
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	22	23	66	68
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(22)	(22)	(65)	(66)
Net periodic cost (benefit)	44	45	131	134
Total periodic cost	44	45	131	134
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	11	11	31	32
Amortization of prior service cost	(19)	(20)	(58)	(60)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(17)	(16)	(50)	(51)
Net periodic cost (benefit)	9	7	23	23
Total periodic cost	9	7	23	23
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	13	14	38	41
Net periodic cost (benefit)	13	14	38	41
Amortization of pre-merger regulatory asset	2	2	6	6
Total periodic cost	$ 15	$ 16	$ 44	$ 47