Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan expense	$ 5.5	$ 5.6	$ 5.3
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Expected contribution	18.9
Expect to recognize unrecognized actuarial gains (losses)	(15.0)
Expect to recognize prior service credit\cost	$ 0.2
Defined Benefit Pension Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.50%	3.90%
Long-term return on plan assets	7.50%	7.50%	7.50%
Weighted average discount rate used in determining the net periodic cost	3.90%	4.10%	3.80%
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%	92.00%
Defined Benefit Pension Plans | Foreign
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.10%	2.10%
Long-term return on plan assets	2.50%	3.90%	4.60%
Weighted average discount rate used in determining the net periodic cost	2.10%	2.60%	2.50%
Defined Benefit Pension Plans | Foreign | Canada
Defined Benefit Plan Disclosure [Line Items]
Average basis points of long-term rate of return on investment	1.25%
Defined Benefit Pension Plans | Foreign | Significant Unobservable Inputs (Level 3) | Norway
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	10.00%
Defined Benefit Pension Plans | Foreign | Equity Securities | Norway
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	6.00%
Percentage of plan asset allocation	11.00%
Defined Benefit Pension Plans | Foreign | Equity Securities | Minimum | Canada
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	20.00%
Defined Benefit Pension Plans | Foreign | Equity Securities | Maximum | Canada
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	30.00%
Defined Benefit Pension Plans | Foreign | Fixed Income Funds | Norway
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 | Foreign | Fixed Income Funds | Minimum | Canada
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	70.00%
Defined Benefit Pension Plans | Foreign | Fixed Income Funds | Maximum | Canada
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan asset allocation	80.00%
Defined Benefit Pension Plans | Foreign | Real Estate | Norway
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 | Foreign | Other Investments And Liquid Funds | Norway
Defined Benefit Plan Disclosure [Line Items]
Long-term return on plan assets	7.00%
OPEB
Defined Benefit Plan Disclosure [Line Items]
Expected contribution	$ 1.0
Discount rate	3.10%	3.40%
Expect to recognize unrecognized actuarial gains (losses)	$ 0.2
Expect to recognize prior service credit\cost	$ 1.1
Eligible age for health care benefits	65 years
Weighted average discount rate used in determining the net periodic cost	3.35%	3.60%	3.40%