Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Asset retirement obligation	$ 3,100	$ 2,800
Gain (loss) on disposal of property and equipment	800	(500)	$ (1,400)
Retail store asset impairment			15,271
SOUTH AFRICA
Property, Plant and Equipment [Line Items]
Additional impairment of assets to be disposed of			5,700
Underperforming Retail Stores
Property, Plant and Equipment [Line Items]
Retail store asset impairment	$ 530	$ 2,713	$ 9,600