Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Defined Contribution and Defined Benefit Retirement - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan expense	$ 6.6	$ 6.5	$ 6.6
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit fair value of plan assets	548.2	498.4
Expected contribution	18.0
Expect to recognize unrecognized actuarial gains (losses)	21.0
Expect to recognize prior service credit\cost	0.2
Defined Benefit Pension Plans \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit fair value of plan assets	314.8	283.5	259.6
Defined Benefit Pension Plans \| Non U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan benefit obligation	855.8	746.4	667.2
Defined benefit fair value of plan assets	494.8	450.0	$ 410.7
Net underfunded status	$ 361.0	$ 296.4
Discount rate	1.00%	1.40%
Long-term return on plan assets	2.00%	2.90%	3.00%
Defined Benefit Pension Plans \| U.K.
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan benefit obligation	$ 12.2
Defined benefit fair value of plan assets	17.3
Defined benefit pension plan assets	$ 5.2
Defined Benefit Pension Plans \| Canada \| Equity Securities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	20.00%
Defined Benefit Pension Plans \| Canada \| Equity Securities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	30.00%
Defined Benefit Pension Plans \| Canada \| Fixed Income Funds \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	70.00%
Defined Benefit Pension Plans \| Canada \| Fixed Income Funds \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	80.00%
Defined Benefit Pension Plans \| Norway \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation		14.00%
Defined Benefit Pension Plans \| Norway \| Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	5.00%
Percentage of plan asset allocation	15.00%
Defined Benefit Pension Plans \| Norway \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	3.00%
Percentage of plan asset allocation	62.00%
Defined Benefit Pension Plans \| Norway \| Real Estate
Defined Benefit Plan Disclosure [Line Items]
Defined benefit fair value of plan assets	$ 7.1	$ 6.6
Long-term return on plan assets	4.00%
Percentage of plan asset allocation	14.00%
Defined Benefit Pension Plans \| Norway \| Real Estate \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit fair value of plan assets	$ 7.1	6.6
Defined Benefit Pension Plans \| Norway \| Other Investments And Liquid Funds
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	7.00%
Defined Benefit Pension Plans \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan benefit obligation	$ 63.2	60.6	$ 57.6
Defined benefit fair value of plan assets	53.3	48.4	$ 43.2
Net underfunded status	$ 9.9	$ 12.2
Discount rate	2.20%	3.10%
Long-term return on plan assets	4.50%	5.50%	7.50%
Defined Benefit Pension Plans \| U.S. \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	34.00%
Defined Benefit Pension Plans \| U.S. \| Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	9.00%
Percentage of plan asset allocation	38.00%
Defined Benefit Pension Plans \| U.S. \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	3.00%
Percentage of plan asset allocation	54.00%
Defined Benefit Pension Plans \| U.S. \| CMRT
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	2.00%