Basis of Presentation and New Accounting Pronouncements (Detail) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Basis Of Presentation And Accounting Policies [Line Items]
Accounts receivable, net of allowance for doubtful accounts	$ 200,024,000	$ 185,058,000
Aggregate amount of transaction price allocated to material rights that remain unsatisfied	$ 2,681,000
Revenue expected to be recognized in next 12 months	33.00%
Revenue expected to be recognized in 2019	52.00%
Revenue expected to be recognized in 2020	11.00%
Revenue expected to be recognized in 2021	4.00%
Unearned revenue	$ 5,768,000	4,889,000
Income tax effects from Tax Act	0	20,153,000
ASU 2018-02
Basis Of Presentation And Accounting Policies [Line Items]
Adjustment against retained earnings for effect of change in federal corporate income tax rate	40,000
Adjustments related to valuation allowance	0
Income tax effects from Tax Act	0
ASU 2014-09
Basis Of Presentation And Accounting Policies [Line Items]
Cash from or used in operating activities	0
Cash from or used in investing activities	0
Cash from or used in financing activities	0
ASU 2016-16
Basis Of Presentation And Accounting Policies [Line Items]
Favourable adjustment to retained earnings	$ 31,645,000
Minimum
Basis Of Presentation And Accounting Policies [Line Items]
Payment terms of contracts	30 days
Maximum
Basis Of Presentation And Accounting Policies [Line Items]
Payment terms of contracts	120 days
Industrial Segments
Basis Of Presentation And Accounting Policies [Line Items]
Unearned revenue	$ 3,087,000	$ 4,889,000

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Deferred revenue expected to be recognized in the next twelve months.

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Deferred revenue expected to be recognized in year four.

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Deferred revenue expected to be recognized in year three.

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Deferred revenue expected to be recognized in year two.

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Tax cuts and jobs act of 2017, incomplete accounting, provisional income tax expense (benefit).

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Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act.

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Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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Amount of cash inflow (outflow) of financing activities, excluding discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) of investing activities, excluding discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, excluding discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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Amount of increase (decrease) in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from adjustments.

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