Acquisitions - Narrative (Details) - USD ($) $ in Thousands			12 Months Ended
	Jul. 01, 2019	Jan. 02, 2019	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill			$ 49,079	$ 47,396
Goodwill expected to be deductible for tax purposes	$ 17,900
Percentage of individuals employed by educational institutions			80.00%
Benefit Consultants Group Inc.
Business Acquisition [Line Items]
Transaction value		$ 25,000
Finite-lived intangible assets acquired		16,200
Goodwill		10,100
Goodwill expected to be deductible for tax purposes		$ 10,100
NTA
Business Acquisition [Line Items]
Transaction value	425,900
Goodwill	19,600
Acquired finite-lived intangible assets, useful lives			23 years
Adjusted earnings consideration	$ 20,900
Minimum | Benefit Consultants Group Inc.
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, useful lives			10 years
Maximum | Benefit Consultants Group Inc.
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, useful lives			16 years