Reportable Segments - Operations of Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Total net service revenues	$ 341,053	$ 336,460	$ 1,015,354	$ 993,708
Gross profit	104,375	105,380	305,429	308,851
Operating expenses	85,395	90,656	259,224	267,663
Income before income taxes	18,980	14,724	46,205	41,188
Flex revenues
Segment Reporting Information [Line Items]
Total net service revenues	328,904	323,484	977,847	954,593
Direct Hire revenues
Segment Reporting Information [Line Items]
Total net service revenues	12,149	12,976		39,115
Tech
Segment Reporting Information [Line Items]
Total net service revenues	229,281	225,524	679,695	666,670
Gross profit	65,560	65,173	192,223	193,132
Tech | Flex revenues
Segment Reporting Information [Line Items]
Total net service revenues	224,148	220,376	663,778	650,997
Tech | Direct Hire revenues
Segment Reporting Information [Line Items]
Total net service revenues	5,133	5,148	15,917
FA
Segment Reporting Information [Line Items]
Total net service revenues	85,225	84,118	260,786	251,807
Gross profit	29,709	30,439	89,666
FA | Flex revenues
Segment Reporting Information [Line Items]
Total net service revenues	78,209	76,290	239,196	228,365
FA | Direct Hire revenues
Segment Reporting Information [Line Items]
Total net service revenues	7,016	7,828	21,590
GS
Segment Reporting Information [Line Items]
Total net service revenues	26,547	26,818	74,873	75,231
Gross profit	9,106	9,768	23,540	25,024
GS | Flex revenues
Segment Reporting Information [Line Items]
Total net service revenues	26,547	26,818	74,873	75,231
GS | Direct Hire revenues
Segment Reporting Information [Line Items]
Total net service revenues	$ 0	$ 0	$ 0	$ 0