Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Income Tax Contingency [Line Items]
Effective income tax rate		45.90%	27.80%
Unrecognized tax benefits that would impact effective tax rate	$ 7.7	$ 7.7				$ 7.6
Interest and penalties accrued	0.5	0.5				$ 0.3
Liability for uncertain tax positions that would impact the effective tax rate if recognized	5.5	$ 5.5
Cumulative provisional net charge due to change to territorial tax system	$ 15.8
United States Internal Revenue Service | Earliest Tax Year
Income Tax Contingency [Line Items]
Tax year remain open to examination		2014
United States Internal Revenue Service | Latest Tax Year
Income Tax Contingency [Line Items]
Tax year remain open to examination		2018
Maximum
Income Tax Contingency [Line Items]
Tax cut and job act measurement period	1 year
State Jurisdictions | Earliest Tax Year
Income Tax Contingency [Line Items]
Tax year remain open to examination		2012
State Jurisdictions | Latest Tax Year
Income Tax Contingency [Line Items]
Tax year remain open to examination		2018
Foreign Taxing Jurisdictions | Earliest Tax Year
Income Tax Contingency [Line Items]
Tax year remain open to examination		2006
Foreign Taxing Jurisdictions | Latest Tax Year
Income Tax Contingency [Line Items]
Tax year remain open to examination		2018
Scenario Forecast
Income Tax Contingency [Line Items]
U.S. statutory rate				21.00%	28.00%