Basis of Presentation and Nature of Operations - Additional Information (Details)	3 Months Ended		9 Months Ended
	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Market Office Segment	Dec. 31, 2019 USD ($)
Basis of Presentation and Nature of Operations [Line Items]
Number of key client markets | Market			4
Number of operating segments | Segment			1
Number of reporting segments | Segment			1
Retained earnings			$ 578,554,000	$ 544,840,000
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Cumulative Effect, Period of Adoption, Adjustment | Revision of Prior Period, Adjustment
Basis of Presentation and Nature of Operations [Line Items]
Retained earnings	$ 500,000
Indirect and Selling Expenses
Basis of Presentation and Nature of Operations [Line Items]
Impairment expense related to intangible assets		$ 1,700,000	$ 0
Domestic | Minimum
Basis of Presentation and Nature of Operations [Line Items]
Number of offices | Office			75
International
Basis of Presentation and Nature of Operations [Line Items]
Number of offices | Office			15