Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 01, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Revenue target	$ 80,000
Contingent obligation due selling unitholders of Cogent		$ 9,456		$ 9,456		$ 15,095
Increase (decrease) in fair value contingent consideration				(5,639)	$ 1,422
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
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
Contingent obligation due selling unitholders of Cogent	$ 13,100	9,600		9,600
Increase (decrease) in fair value contingent consideration		$ 1,900	$ 30	$ (5,600)	$ 1,400