Goodwill and intangible assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 10, 2017
Indefinite-lived Intangible Assets [Line Items]
Goodwill	$ 47,803,000	$ 49,464,000
Amortization of Intangible Assets	2,973,000	1,107,000	$ 488,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	3,000,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	3,000,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	2,900,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	2,900,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	2,900,000
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	14,800,000
Goodwill, Impairment Loss	0	0	0
Airgas Refrigerants, Inc. [Member]
Indefinite-lived Intangible Assets [Line Items]
Goodwill				$ 47,000,000
Amortization of Intangible Assets	$ 3,000,000	$ 1,100,000	$ 500,000
Polar Technologies Llc [Member]
Indefinite-lived Intangible Assets [Line Items]
Goodwill				400,000
Supplier [Member]
Indefinite-lived Intangible Assets [Line Items]
Goodwill				$ 400,000