Employee Benefit Plans - Employee Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Document Period End Date			Sep. 30, 2015
Amortization of prior service cost	$ (17)	$ (14)	$ (50)	$ (44)
Amortization of net loss	249	65	745	198
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	15	17	45	50
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Amortization of net loss	2	0	5	0
Net periodic cost (benefit)	17	17	50	50
Amortization of pre-merger regulatory asset	2	2	6	6
Total periodic cost	19	19	56	56
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	11	13	33	39
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(19)	(19)	(58)	(58)
Amortization of net loss	17	16	53	50
Net periodic cost (benefit)	9	10	28	31
Amortization of pre-merger regulatory asset	0	0	0	0
Total periodic cost	9	10	28	31
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	23	23	68	69
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	2	5	8	14
Amortization of net loss	25	12	74	36
Net periodic cost (benefit)	50	40	150	119
Amortization of pre-merger regulatory asset	0	0	0	0
Total periodic cost	50	40	150	119
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	626	647	1,877	1,941
Expected return on plan assets	(777)	(773)	(2,330)	(2,318)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	114	0	341	0
Net periodic cost (benefit)	(37)	(126)	(112)	(377)
Amortization of pre-merger regulatory asset	191	191	571	571
Total periodic cost	154	65	459	194
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	102	107	306	320
Expected return on plan assets	(135)	(133)	(405)	(398)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	91	37	272	112
Net periodic cost (benefit)	58	11	173	34
Amortization of pre-merger regulatory asset	0	0	0	0
Total periodic cost	$ 58	$ 11	$ 173	$ 34