Commitments and contingencies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020 site claim location
Other Commitments [Line Items]
Number of locations impacted by environmental laws and regulations | location	129
Number of company owned/occupied sites requiring environmental remediation work	107
Number of non owned sites liable for a share of clean-up	22
Maximum
Other Commitments [Line Items]
Number of asbestos-related claims (fewer than) | claim	150
Environmental project, term	30 years
Minimum
Other Commitments [Line Items]
Environmental project, term	2 years