Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 358,624	$ 340,309	$ 704,917	$ 674,301
Gross profit	107,483	103,919	207,671	201,054
Operating expenses	85,641	85,916	173,580	173,829
Income before income taxes	21,842	18,003	34,091	27,225
Tech
Segment Reporting Information [Line Items]
Revenue	249,763	228,369	486,260	450,414
Gross profit	71,830	65,563	137,178	126,663
FA
Segment Reporting Information [Line Items]
Revenue	79,772	88,266	160,716	175,561
Gross profit	28,390	31,302	55,551	59,957
GS
Segment Reporting Information [Line Items]
Revenue	29,089	23,674	57,941	48,326
Gross profit	$ 7,263	$ 7,054	$ 14,942	$ 14,434

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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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 32
-Paragraph 2A
-URI http://asc.fasb.org/extlink&oid=82859839&loc=SL82860478-203043

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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