Employee Benefit Plans - Amounts Included in Regulatory Asset and Accumulated Other Comprehensive Income/Loss Recognized as Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (20)	$ (58)	$ (60)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		277	274	826	815
Recognized from accumulated other comprehensive loss	[1]	152	146	451	440
Recognized from regulatory asset		106	108	317	315
Total recognized in net periodic benefit cost		258	254	768	755
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		107	103	319	309
Recognized from accumulated other comprehensive loss	[1]	107	103	319	309
Total recognized in net periodic benefit cost		107	103	319	309
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		131	133	392	389
Recognized from accumulated other comprehensive loss	[1]	25	25	75	74
Recognized from regulatory asset		106	108	317	315
Total recognized in net periodic benefit cost		131	133	392	389
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		22	22	65	66
Recognized from accumulated other comprehensive loss	[1]	22	22	65	66
Total recognized in net periodic benefit cost		22	22	65	66
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(20)	(58)	(60)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		17	16	50	51
Recognized from accumulated other comprehensive loss	[1]	(2)	(4)	(8)	(9)
Total recognized in net periodic benefit cost		$ (2)	$ (4)	$ (8)	$ (9)

[1] See Note 7, Stockholder's Equity.