Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Apr. 01, 2015	Jun. 30, 2018	Jun. 30, 2019	Jun. 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		$ 18,293
Increase (decrease) in fair value contingent consideration			575	$ 3,591
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
Contingent obligation due selling unitholders of Cogent	$ 13,100
Increase (decrease) in fair value contingent consideration		$ 2,700	$ 600	$ 3,600