Defined Contribution and Defined Benefit Retirement - Composition of Pension Plan Assets (Detail) - Defined Benefit Pension Plans - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 498.4	$ 454.0
Foreign
Defined Benefit Plan Disclosure [Line Items]
Plan assets	450.0	410.7	$ 445.2
Germany
Defined Benefit Plan Disclosure [Line Items]
Plan assets	264.5	241.5
Canada | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.3	6.5
Canada | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16.3	13.3
Canada | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	80.9	74.1
Canada | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.6	0.5
Norway | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1.6	1.7
Norway | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.2	4.3
Norway | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	22.8	20.4
Norway | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.2	13.5
Norway | Non Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.3	6.1
Norway | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.6	4.5
Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	27.6	24.4
U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets	48.4	43.2	46.5
U.S. | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.0	4.7
U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	19.2	16.3
U.S. | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	23.3	19.9
U.S. | CMRT
Defined Benefit Plan Disclosure [Line Items]
Plan assets		2.3
Quoted Prices in Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	191.6	176.2
Quoted Prices in Active Markets (Level 1) | Canada | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.3	6.5
Quoted Prices in Active Markets (Level 1) | Canada | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16.3	13.3
Quoted Prices in Active Markets (Level 1) | Canada | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	80.9	74.1
Quoted Prices in Active Markets (Level 1) | Canada | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.6	0.5
Quoted Prices in Active Markets (Level 1) | Norway | Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1.6	1.7
Quoted Prices in Active Markets (Level 1) | Norway | Non Local Currency Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.2	4.3
Quoted Prices in Active Markets (Level 1) | Norway | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	14.1	14.9
Quoted Prices in Active Markets (Level 1) | Norway | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	7.4	12.7
Quoted Prices in Active Markets (Level 1) | Norway | Non Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.3	6.1
Quoted Prices in Active Markets (Level 1) | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16.6	13.9
Quoted Prices in Active Markets (Level 1) | U.S. | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4.6	3.4
Quoted Prices in Active Markets (Level 1) | U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	5.4	4.9
Quoted Prices in Active Markets (Level 1) | U.S. | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	23.3	19.9
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.7	5.5
Significant Other Observable Inputs (Level 2) | Norway | Local Currency Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	8.7	5.5
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	283.5	259.6	$ 273.6
Significant Unobservable Inputs (Level 3) | Germany
Defined Benefit Plan Disclosure [Line Items]
Plan assets	264.5	241.5
Significant Unobservable Inputs (Level 3) | Norway | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.8	0.8
Significant Unobservable Inputs (Level 3) | Norway | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6.6	4.5
Significant Unobservable Inputs (Level 3) | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	11.0	10.5
Significant Unobservable Inputs (Level 3) | U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.6
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	14.6	12.7
Assets measured at NAV | U.S. | Cash and Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1.4	1.3
Assets measured at NAV | U.S. | Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 13.2	$ 11.4