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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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

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Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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

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Percentage of investment to total investment within defined benefit plan asset category.

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Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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Amount of cost for defined contribution plan.

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Combined master retirement trust asset fair value input percentage.

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Defined benefit plan expected return on investment spread above index return.

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Defined Contribution and Defined Benefit Retirement - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan expense	$ 6.6	$ 5.5	$ 5.6
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Expected contribution	18.2
Expect to recognize unrecognized actuarial gains (losses)	15.6
Expect to recognize prior service credit\cost	$ 0.2
Defined Benefit Pension Plans \| Foreign
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.10%	2.10%
Long-term return on plan assets	3.00%	2.50%	3.90%
Defined Benefit Pension Plans \| Canada
Defined Benefit Plan Disclosure [Line Items]
Average basis points of long-term rate of return on investment	1.25%
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	10.00%
Defined Benefit Pension Plans \| Norway \| Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	7.00%
Percentage of plan asset allocation	11.00%
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	79.00%
Defined Benefit Pension Plans \| Norway \| Real Estate
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	5.00%
Percentage of plan asset allocation	7.00%
Defined Benefit Pension Plans \| Norway \| Other Investments And Liquid Funds
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	8.00%
Defined Benefit Pension Plans \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.10%	3.50%
Long-term return on plan assets	7.50%	7.50%	7.50%
Defined Benefit Pension Plans \| U.S. \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	29.00%
Defined Benefit Pension Plans \| U.S. \| CMRT
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	3.00%
Defined Benefit Pension Plans \| U.S. \| CMRT \| Level 1 and Level 2
Defined Benefit Plan Disclosure [Line Items]
Percentage of fair value of asset		93.00%
Defined Benefit Pension Plans \| U.S. \| CMRT \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan investment	6.00%
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	40.00%
Defined Benefit Pension Plans \| U.S. \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	5.00%
Percentage of plan asset allocation	45.00%