Property and Equipment - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets
Intangible Assets	$ 121,304	$ 132,434
Accumulated Amortization	(99,304)	(103,484)
Amortization expenses	$ 7,000	8,000	$ 8,000
Minimum
Intangible Assets
Useful life	5 years
Maximum
Intangible Assets
Useful life	20 years
Technology-based
Intangible Assets
Intangible Assets	$ 58,162	58,162
Accumulated Amortization	(47,746)	(44,289)
Trademarks
Intangible Assets
Intangible Assets	35,010	46,140
Accumulated Amortization	(23,426)	(31,063)
Contract-based
Intangible Assets
Intangible Assets	4,500	4,500
Accumulated Amortization	(4,500)	(4,500)
Customer relationships
Intangible Assets
Intangible Assets	23,632	23,632
Accumulated Amortization	$ (23,632)	$ (23,632)