Revenue Recognition - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Cumulative effect of new accounting standard, net of tax						$ (179)
Contingency period (or less)			90 days
Required payment period (typically less)			90 days
Contract assets	$ 0		$ 0		$ 0
Contract liabilities	0		0		0
Direct Hire revenue
Disaggregation of Revenue [Line Items]
Contract with customer, refund liability	$ 500		$ 500			500
Fixed-price Contract | GS | Flex revenue
Disaggregation of Revenue [Line Items]
Revenue, as a percent	42.30%	30.90%	41.40%	29.90%
Retained Earnings
Disaggregation of Revenue [Line Items]
Cumulative effect of new accounting standard, net of tax						$ (179)
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Contract liabilities					200
Accounting Standards Update 2014-09 | Retained Earnings
Disaggregation of Revenue [Line Items]
Cumulative effect of new accounting standard, net of tax					$ (200)