Other Income, net - Summary of Other Income, net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Income and Expenses [Abstract]
Interest and dividend income	$ 322	$ 354	$ 1,317	$ 1,208
Gain on mutual fund investments	2,556	2,562	6,777	6,191
Change in fair value of earn-out consideration	0	0	0	4,060
Other, net	44	(25)	777	738
Other income, net	$ 2,922	$ 2,891	$ 8,871	$ 12,197