Income Taxes - Components of Income Taxes and Comprehensive Provision for Income Taxes Allocation (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Schedule Of Income Tax [Line Items]          
U.S.     $ 11.5 $ 5.5 $ 59.2
Non-U.S.     49.7 (36.3) 74.5
Income (loss) before income taxes     61.2 (30.8) 133.7
Expected tax expense (benefit), at U.S. federal statutory income tax rate of 35%     21.4 (10.8) 46.8
Non-U.S. tax rates     (4.3) 0.5 (4.2)
Incremental net tax (benefit) on earnings and losses of non-U.S. companies     2.2 (8.7) (3.7)
Valuation allowance     (2.2) 159.0  
Adjustment to the reserve for uncertain tax positions, net $ 2.4   2.4 0.7 (5.1)
Nondeductible expenses     1.5 2.1 1.9
U.S. state income taxes and other, net     0.3   (1.2)
Provision for income taxes     17.9 142.8 34.5
Currently payable:          
U.S. federal and state       0.3 1.9
Non-U.S.     9.5 3.3 15.2
Total     9.5 3.6 17.1
Deferred income taxes (benefit):          
U.S. federal and state     4.3 (6.4) 10.0
Non-U.S.     4.1 145.6 7.4
Total     8.4 139.2 17.4
Comprehensive provision for income taxes (benefit) allocable to:          
Net income     17.9 142.8 34.5
Other comprehensive income (loss):          
Currency translation         (16.9)
Marketable securities     1.3 1.1 (6.7)
Interest rate swap     0.2 (1.3)  
Total     18.4 144.0 (19.6)
Defined Benefit Pension Plans          
Other comprehensive income (loss):          
Benefit plans     (0.8) 1.5 (30.1)
OPEB          
Other comprehensive income (loss):          
Benefit plans     (0.2) $ (0.1) $ (0.4)
US-Canada APA          
Schedule Of Income Tax [Line Items]          
U.S. - Canada APA $ 2.2 $ (5.6) $ (3.4)