Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 01, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Revenue target	$ 80,000
Distribution period ending on the second anniversary of the closing (years)	2 years
Distribution period ending on the fourth anniversary of the closing (years)	2 years
Distribution period ending On March 31 2017 (years)	2 years
Distribution period ending On March 31 2019 (years)	2 years
Contingent obligation due selling unitholders of Cogent		$ 0		$ 0		$ 18,293
Increase (decrease) in fair value contingent consideration				$ 575	$ 4,022
Cogent Partners, LP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maximum contingent consideration	$ 18,900
Conditional consideration (shares)	334,048	334,048	334,048	334,048	334,048
Contingent obligation due selling unitholders of Cogent	$ 13,100
Increase (decrease) in fair value contingent consideration			$ 400	$ 600	$ 4,000