Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2019	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Statutory federal income tax rate	21.00%			21.00%			35.00%
Decrease in benefit associated with settlement of tax audits and ancillary issues	$ 3.2			$ 3.4
Undistributed earnings of foreign subsidiaries			$ 531.8				$ 531.8
Canada Revenue Agency [Member]
Income Tax [Line Items]
Income tax benefit recognized on settlement of Canadian audit		$ (2.7)			$ (1.2)
US 2017 Tax Reform Act [Member]
Income Tax [Line Items]
Statutory federal income tax rate						21.00%
Additional income tax expense/benefit attributable to the enactment of the 2017 Tax Reform Act			32.7			$ (0.2)	32.7
US 2017 Tax Reform Act [Member] | One-Time Transition Tax on Mandatory Deemed Repatriation of Foreign Earnings [Member]
Income Tax [Line Items]
Additional income tax expense/benefit attributable to the enactment of the 2017 Tax Reform Act			32.7				32.7
US 2017 Tax Reform Act [Member] | Foreign Withholding Taxes on Certain Anticipated Distributions [Member]
Income Tax [Line Items]
Additional income tax expense/benefit attributable to the enactment of the 2017 Tax Reform Act			1.0				1.0
US 2017 Tax Reform Act [Member] | Remeasurement of Certain Deferred Tax Assets and Liabilities [Member]
Income Tax [Line Items]
Additional income tax expense/benefit attributable to the enactment of the 2017 Tax Reform Act			$ (1.0)				$ (1.0)