Defined Contribution and Defined Benefit Retirement - Composition of Pension Plan Assets (Detail) - Defined Benefit Pension Plans - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 454.0	$ 491.7
Foreign
Defined Benefit Plan Disclosure [Line Items]
Plan assets	410.7	445.2	$ 381.8
Germany
Defined Benefit Plan Disclosure [Line Items]
Plan assets	241.5	257.9
Canada | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.5	8.4
Canada | Foreign Equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets		16.4
Canada | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	74.1	81.8
Canada | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.5	0.3
Canada | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	13.3
Norway | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1.7	1.8
Norway | Foreign Equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets		4.6
Norway | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	20.4	21.0
Norway | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	13.5	15.4
Norway | Foreign Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets		6.8
Norway | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.5	4.7
Norway | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.3
Norway | Non Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.1
Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	24.4	26.1
U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets	43.2	46.5	45.6
U.S. | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.7
U.S. | CMRT
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2.3	46.5
U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16.3
U.S. | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	19.9
Quoted Prices in Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	176.2	171.6
Quoted Prices in Active Markets (Level 1) | Canada | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.5	8.4
Quoted Prices in Active Markets (Level 1) | Canada | Foreign Equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets		16.4
Quoted Prices in Active Markets (Level 1) | Canada | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	74.1	81.8
Quoted Prices in Active Markets (Level 1) | Canada | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.5	0.3
Quoted Prices in Active Markets (Level 1) | Canada | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	13.3
Quoted Prices in Active Markets (Level 1) | Norway | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1.7	1.8
Quoted Prices in Active Markets (Level 1) | Norway | Foreign Equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets		4.6
Quoted Prices in Active Markets (Level 1) | Norway | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	14.9	21.0
Quoted Prices in Active Markets (Level 1) | Norway | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	12.7	14.5
Quoted Prices in Active Markets (Level 1) | Norway | Foreign Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets		6.8
Quoted Prices in Active Markets (Level 1) | Norway | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.3
Quoted Prices in Active Markets (Level 1) | Norway | Non Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.1
Quoted Prices in Active Markets (Level 1) | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	13.9	16.0
Quoted Prices in Active Markets (Level 1) | U.S. | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	3.4
Quoted Prices in Active Markets (Level 1) | U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.9
Quoted Prices in Active Markets (Level 1) | U.S. | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	19.9
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	5.5	46.5
Significant Other Observable Inputs (Level 2) | Norway | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	5.5
Significant Other Observable Inputs (Level 2) | U.S. | CMRT
Defined Benefit Plan Disclosure [Line Items]
Plan assets		46.5
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	259.6	273.6	$ 230.5
Significant Unobservable Inputs (Level 3) | Germany
Defined Benefit Plan Disclosure [Line Items]
Plan assets	241.5	257.9
Significant Unobservable Inputs (Level 3) | Norway | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.8	0.9
Significant Unobservable Inputs (Level 3) | Norway | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.5	4.7
Significant Unobservable Inputs (Level 3) | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	10.5	$ 10.1
Significant Unobservable Inputs (Level 3) | U.S. | CMRT
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2.3
Assets measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Plan assets	12.7
Assets measured at NAV | U.S. | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1.3
Assets measured at NAV | U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 11.4