Business Combinations - Additional Information (Detail) $ in Thousands												3 Months Ended		9 Months Ended
	Aug. 15, 2016 USD ($)	Jul. 25, 2016 USD ($)	Apr. 12, 2016 USD ($)	Feb. 29, 2016 USD ($)	Feb. 02, 2016 USD ($)	Jan. 25, 2016 USD ($)	Aug. 10, 2015 USD ($)	Jul. 01, 2015 USD ($)	Jun. 01, 2015 USD ($)	Apr. 06, 2015 USD ($)	Mar. 12, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Business	Sep. 30, 2015 USD ($) Business
Business Acquisition [Line Items]
Business combinations | Business														6	5
Goodwill acquired expected to be tax deductible												$ 12,800	$ 22,100	$ 12,800	$ 22,100
Purchase price paid in cash														36,427	71,040
Seller obligations in connection with acquisition of businesses														2,849	12,364
Revenue												225,392	181,579	629,003	471,220
Net income (loss)														27,355	17,230
Amortization of intangibles												2,889	1,817	8,178	4,091
Income tax expense (benefit)												6,723	4,869	14,792	9,612
Key Insulation [Member]
Business Acquisition [Line Items]
Purchase price paid in cash						$ 5,000
Seller obligations in connection with acquisition of businesses						$ 700
Revenue												2,000		6,300
Net income (loss)												(200)		(400)
Marshall Insulation LLC [Member]
Business Acquisition [Line Items]
Purchase price paid in cash					$ 900
Seller obligations in connection with acquisition of businesses					$ 100
Revenue												1,000		2,500
Net income (loss)												(54)		(200)
Kern Door Company [Member]
Business Acquisition [Line Items]
Purchase price paid in cash				$ 2,900
Seller obligations in connection with acquisition of businesses				$ 100
Revenue												1,000		2,000
Net income (loss)												(62)		(200)
BDI Insulation [Member]
Business Acquisition [Line Items]
Purchase price paid in cash											$ 30,700
Seller obligations in connection with acquisition of businesses											$ 5,800				5,765
Revenue													10,300		22,500
Net income (loss)													600		1,600
Ownership percentage acquired											100.00%
Insurance receivable for claims under a fully insured policy												2,000	2,000	2,000	2,000
Indemnification asset associated with the acquisition												1,600	1,600	1,600	1,600
Combined Business Acquisitions [Member]
Business Acquisition [Line Items]
Seller obligations in connection with acquisition of businesses														2,849	12,103
Amortization of intangibles												37	1,200	700	4,900
Income tax expense (benefit)												100	300	18	1,200
Transaction costs													1,000		1,000
Alpine [Member]
Business Acquisition [Line Items]
Purchase price paid in cash			$ 21,200
Seller obligations in connection with acquisition of businesses			$ 1,600											1,560
Revenue												7,900		14,700
Net income (loss)												800		1,200
FireClass, LLC [Member]
Business Acquisition [Line Items]
Purchase price paid in cash		$ 2,300
Revenue												800		800
Net income (loss)												21		21
Southern Insulators & Specialties LLC [Member]
Business Acquisition [Line Items]
Purchase price paid in cash	$ 4,100
Seller obligations in connection with acquisition of businesses	$ 400
Revenue												700		700
Net income (loss)												$ 100		$ 100
CQ Insulation [Member]
Business Acquisition [Line Items]
Purchase price paid in cash										$ 5,200
Seller obligations in connection with acquisition of businesses										$ 2,300					2,319
Revenue													2,700		5,400
Net income (loss)													300		500
Ownership percentage acquired										100.00%
Layman Brothers Contracting [Member]
Business Acquisition [Line Items]
Purchase price paid in cash									$ 9,100
Seller obligations in connection with acquisition of businesses									$ 600						600
Revenue													3,700		4,900
Net income (loss)													300		400
EcoLogic Energy Solutions [Member]
Business Acquisition [Line Items]
Purchase price paid in cash								$ 3,000
Seller obligations in connection with acquisition of businesses								$ 500
Revenue													1,800		1,800
Net income (loss)													36		36
Eastern Contractor Services [Member]
Business Acquisition [Line Items]
Purchase price paid in cash							$ 24,200
Seller obligations in connection with acquisition of businesses							$ 2,900								2,875
Revenue													3,000		3,000
Net income (loss)													$ 300		$ 300
Ownership percentage acquired							100.00%