Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	$ 83,830	$ 83,830
Finite-Lived Intangible Assets, Accumulated Amortization	(60,065)	(56,035)
Finite-Lived Intangible Assets, Net	23,765	27,795
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	(14,535)	(11,164)
Finite-Lived Intangible Assets, Net	$ 20,126	$ 23,497
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 11 months	7 years 4 months
Trade Names
Acquired Finite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	$ 6,381	$ 6,381
Finite-Lived Intangible Assets, Accumulated Amortization	(2,742)	(2,083)
Finite-Lived Intangible Assets, Net	$ 3,639	$ 4,298
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years 6 months	5 years 2 months