Revenues (Net Profits on Inventory Sales Included in Commissions) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues [Abstract]
Revenue from inventory sales	$ 111,032	$ 150,147	$ 235,589	$ 303,428
Cost of inventory sold	(104,978)	(136,255)	(216,514)	(274,832)
Net profits on inventory	$ 6,054	$ 13,892	$ 19,075	$ 28,596