Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Expected pension and postretirement benefit costs		$ 856
Expected amortization of pre merger regulatory asset		769
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Unamortized balance of regulatory asset	$ 749	749	$ 1,300
Contribution to pension plan	123	971
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	1,500	1,500
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	235	433
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	359	359
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	38	113
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	151	151
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan		15
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	97	97
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	9	33
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 88	$ 88