Goodwill and Other Intangible Assets - Schedule of Carrying Value and Accumulated Amortization of Intangible Assets (Detail) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 13,777	$ 12,365
Accumulated Amortization		5,485	4,236
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	10,680	9,391
Accumulated Amortization	[1]	4,269	3,463
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	2,375	2,252
Accumulated Amortization	[1]	768	451
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		452	452
Accumulated Amortization		236	118
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		270	270
Accumulated Amortization		$ 212	$ 204

[1] 1) The customer relationship and non-compete agreements amounts includes $1.3 million and $0.1 million, respectively, recorded as a result of the purchase of the operating assets of Western Natural Gas in October 2020. The amounts also include customer relationship and non-compete agreements amounts of $4.6 million and $0.5 million, respectively, recorded as a result of the purchase of the operating assets of Boulden in December 2019.