Revenues (Net Profits on Inventory Sales Included in Commissions) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues [Abstract]
Revenue from inventory sales	$ 76,048	$ 124,557
Cost of inventory sold	(63,401)	(111,536)
Net profits on inventory	$ 12,647	$ 13,021