Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning balance	$ 210,885	$ 209,793
Foreign currency translation adjustments	(927)	1,092
Ending balance	209,958	210,885
Temporary and consultant staffing
Goodwill [Roll Forward]
Beginning balance	134,488	133,875
Foreign currency translation adjustments	(421)	613
Ending balance	134,067	134,488
Permanent placement staffing
Goodwill [Roll Forward]
Beginning balance	26,159	26,015
Foreign currency translation adjustments	(101)	144
Ending balance	26,058	26,159
Risk consulting and internal audit services
Goodwill [Roll Forward]
Beginning balance	50,238	49,903
Foreign currency translation adjustments	(405)	335
Ending balance	$ 49,833	$ 50,238

Amount of increase (decrease) from foreign currency translation adjustments and purchase accounting adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e961-128460

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

Name:	us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration