Employee Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	$ (20)	$ (17)	$ (60)	$ (50)
Amortization of net loss	274	249	815	745
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	105	102	315	306
Expected return on plan assets	(131)	(135)	(392)	(405)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	103	91	309	272
Net periodic cost (benefit)	77	58	232	173
Amortization of pre-merger regulatory asset	0	0	0	0
Total periodic cost	77	58	232	173
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	635	626	1,894	1,877
Expected return on plan assets	(625)	(777)	(2,027)	(2,330)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	133	114	389	341
Net periodic cost (benefit)	143	(37)	256	(112)
Amortization of pre-merger regulatory asset	191	191	571	571
Total periodic cost	334	154	827	459
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	23	23	68	68
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	2	0	8
Amortization of net loss	22	25	66	74
Net periodic cost (benefit)	45	50	134	150
Amortization of pre-merger regulatory asset	0	0	0	0
Total periodic cost	45	50	134	150
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	11	11	32	33
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(20)	(19)	(60)	(58)
Amortization of net loss	16	17	51	53
Net periodic cost (benefit)	7	9	23	28
Amortization of pre-merger regulatory asset	0	0	0	0
Total periodic cost	7	9	23	28
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	14	15	41	45
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Amortization of net loss	0	2	0	5
Net periodic cost (benefit)	14	17	41	50
Amortization of pre-merger regulatory asset	2	2	6	6
Total periodic cost	$ 16	$ 19	$ 47	$ 56