Intangible Assets Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross	$ 169,762	$ 171,889
Accumulated Amortization	(162,900)	(154,314)
Net	6,862	17,575
Amortization of Intangible Assets	$ 10,700	12,700	$ 12,900
Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Purchased Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	$ 114,754	114,754
Accumulated Amortization	(110,674)	(102,967)
Net	4,080	11,787
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	6,472	6,472
Accumulated Amortization	(6,472)	(6,472)
Net	0	0
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	37,000	37,000
Accumulated Amortization	(37,000)	(34,784)
Net	0	2,216
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	11,536	11,536
Accumulated Amortization	(8,754)	(7,964)
Net	$ 2,782	3,572
Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Gross		2,127
Accumulated Amortization		$ (2,127)