Summary of significant accounting policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Weighted average amortization period of intangible assets, in years	13 years
Reserve for estimated rebates	$ 12.2	$ 11.6
Minimum | Intellectual property
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	7 years
Minimum | Customer relationships
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	8 years
Minimum | Distribution rights
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	10 years
Minimum | Trade names
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	5 years
Minimum | Non-complete Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	2 years
Maximum | Intellectual property
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	20 years
Maximum | Customer relationships
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	27 years
Maximum | Distribution rights
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	17 years
Maximum | Trade names
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	30 years
Maximum | Non-complete Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of Intangible assets, in years	6 years
Building
Summary Of Significant Accounting Policies [Line Items]
Useful life of plant and equipment, in years	30 years
Machinery and Equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life of plant and equipment, in years	3 years
Machinery and Equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life of plant and equipment, in years	10 years
Computer Equipment and Software | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life of plant and equipment, in years	3 years
Computer Equipment and Software | Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life of plant and equipment, in years	5 years
Allowance for Sales Returns
Summary Of Significant Accounting Policies [Line Items]
Reserve for returns and allowances	$ 4.2	$ 4.4