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		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		$ (19)	$ (20)	$ (39)	$ (39)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		236	276	473	551
Recognized from accumulated other comprehensive loss	[1]	130	150	258	300
Recognized from regulatory asset		87	106	176	212
Total recognized in net periodic benefit cost		217	256	434	512
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		88	106	176	213
Recognized from accumulated other comprehensive loss	[1]	88	106	176	213
Total recognized in net periodic benefit cost		88	106	176	213
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)		108	131	217	262
Recognized from accumulated other comprehensive loss	[1]	21	25	41	50
Recognized from regulatory asset		87	106	176	212
Total recognized in net periodic benefit cost		108	131	217	262
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		25	22	50	44
Recognized from accumulated other comprehensive loss	[1]	25	22	50	44
Total recognized in net periodic benefit cost		25	22	50	44
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)		(19)	(20)	(39)	(39)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		15	17	30	32
Recognized from accumulated other comprehensive loss	[1]	(4)	(3)	(9)	(7)
Total recognized in net periodic benefit cost		$ (4)	$ (3)	$ (9)	$ (7)

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