Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Expected pension and postretirement benefit costs	$ 900
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	1,100	$ 1,300
Contribution to pension plan	309
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	1,500
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	72
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	359
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	38
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	151
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	12
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	97
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to pension plan	11
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 88