Reportable Segments - Operations of Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 346,293	$ 333,992
Gross profit	100,188	97,135
Operating expenses	87,939	87,913
Income before income taxes	12,249	9,222
Tech
Segment Reporting Information [Line Items]
Revenue	236,497	222,045
Gross profit	65,348	61,100
FA
Segment Reporting Information [Line Items]
Revenue	80,944	87,295
Gross profit	27,161	28,655
GS
Segment Reporting Information [Line Items]
Revenue	28,852	24,652
Gross profit	$ 7,679	$ 7,380

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1,2)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Amount, before tax, of income (loss) attributable to parent. Includes, but is not limited to, income (loss) from continuing operations, discontinued operations and equity method investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.20)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

+ References

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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