Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)		12 Months Ended
	Aug. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill		$ 25,837,000	$ 19,604,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months		1,139,000
Amortization of intangible assets		818,000	$ 537,000	$ 380,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four		820,000
Amortization of intangible assets, 2019		1,139,102
Amortization of intangible assets, 2020		1,074,245
Amortization of intangible assets, 2022		$ 813,000
ARM [Member] | Unregulated Energy
Goodwill [Line Items]
Goodwill, Acquired During Period	$ 4,300,000
Customer list | Minimum
Goodwill [Line Items]
Amortized period of acquired intangible assets		5 years
Customer list | Maximum
Goodwill [Line Items]
Amortized period of acquired intangible assets		41 years