Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	$ 83,830	$ 83,830
Finite-Lived Intangible Assets, Accumulated Amortization	(64,614)	(61,390)
Finite-Lived Intangible Assets, Net	19,216	22,440
Value of Business Acquired
Acquired Finite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	42,788	42,788
Finite-Lived Intangible Assets, Accumulated Amortization	(42,788)	(42,788)
Finite-Lived Intangible Assets, Net	0	0
Customer Relationships
Acquired Finite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	34,661	34,661
Finite-Lived Intangible Assets, Accumulated Amortization	(18,275)	(15,658)
Finite-Lived Intangible Assets, Net	$ 16,386	$ 19,003
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 4 months	6 years 10 months
Trade Names
Acquired Finite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	$ 6,381	$ 6,381
Finite-Lived Intangible Assets, Accumulated Amortization	(3,551)	(2,944)
Finite-Lived Intangible Assets, Net	$ 2,830	$ 3,437
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 years 6 months	4 years 4 months