Acquisition (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Apr. 01, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Contingent obligation due selling unitholders of Cogent		$ 15,104		$ 15,104		$ 13,647
Increase in fair value contingent consideration				1,457	$ 0
Cogent Partners, LP
Business Acquisition [Line Items]
Ownership percent acquired	100.00%
Amortization expense		100	$ 200	300	$ 200
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
Increase in fair value contingent consideration		$ 1,100		$ 1,500
Ratio of compensation to total revenue, percent					54.00%
Cogent Partners, LP | Minimum
Business Acquisition [Line Items]
Estimated remaining useful life (years)	1 year
Cogent Partners, LP | Maximum
Business Acquisition [Line Items]
Estimated remaining useful life (years)	3 years