Intangible Assets Gross Carrying Amount and Accumulated Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 769,851	$ 669,896	$ 702,507
Accumulated Amortization	(674,623)	(597,745)
Net	95,228	72,151
Core-developed technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	429,548	372,568
Accumulated Amortization	(399,969)	(354,878)
Net	29,579	17,690
Customer contracts and relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	258,586	224,467
Accumulated Amortization	(197,582)	(170,056)
Net	61,004	54,411
Trademarks and Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	70,056	61,785
Accumulated Amortization	(66,004)	(61,766)
Net	4,052	19
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	11,661	11,076
Accumulated Amortization	(11,068)	(11,045)
Net	$ 593	$ 31