Income Taxes - Summary of Income Tax Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax expense (benefit):
Deferred Income Tax Expense (Benefit), Total	$ (8.9)	$ (3.9)	$ (2.1)
Income Tax Expense (Benefit), Total	(7.8)	(0.6)	(9.1)
Continuing Operations
Current income tax expense (benefit):
Federal	(1.2)	(1.5)	(13.9)
State	0.1	0.2	0.4
Foreign	2.6	3.2	6.5
Total current income tax expense (benefit)	1.5	1.9	(7.0)
Deferred income tax expense (benefit):
Federal	(8.9)	(1.6)	1.3
State	(0.2)	0.2	(0.1)
Foreign	(0.2)	(1.1)	(3.3)
Deferred Income Tax Expense (Benefit), Total	(9.3)	(2.5)	(2.1)
Income Tax Expense (Benefit), Total	$ (7.8)	$ (0.6)	$ (9.1)