Acquisition (Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2020	Jan. 02, 2019
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross	$ 62,287	$ 61,595
Amortization of Intangible Assets	13,000	$ 13,100	$ 5,000
Quarton
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross					$ 22,200
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		2 years 9 months 18 days
Amortization of Intangible Assets	$ 8,900	$ 8,900
Intangible assets					22,200
MHT Partners [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross				$ 1,224
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years 2 months 1 day
Amortization of Intangible Assets	$ 100
Intangible assets				1,200
Trade name
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross	$ 1,031	$ 960
Finite-Lived Intangible Asset, Useful Life	3 years
Trade name | Quarton
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross					900
Finite-Lived Intangible Asset, Useful Life		3 years
Trade name | MHT Partners [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross				131
Finite-Lived Intangible Asset, Useful Life		3 years
Customer relationships
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross	$ 52,040	$ 51,724
Customer relationships | Quarton
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross					7,100
Finite-Lived Intangible Asset, Useful Life		4 years
Customer relationships | MHT Partners [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross				749
Finite-Lived Intangible Asset, Useful Life		4 years
Backlog | Quarton
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross					12,600
Finite-Lived Intangible Asset, Useful Life		2 years
Proprietary software | Quarton
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross					$ 1,600
Finite-Lived Intangible Asset, Useful Life		3 years
Noncompete Agreements [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross	$ 344	$ 400
Finite-Lived Intangible Asset, Useful Life	5 years
Noncompete Agreements [Member] | MHT Partners [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross				$ 344
Finite-Lived Intangible Asset, Useful Life		5 years