Revenues (Net Profits on Inventory Sales Included in Commissions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues [Abstract]
Revenue from inventory sales	$ 555,827	$ 758,437	$ 634,498
Cost of inventory sold	(511,892)	(709,072)	(571,993)
Net profits on inventory	$ 43,935	$ 49,365	$ 62,505