Intangible Assets and Liabilities Gross Carrying Amount and Accumulated Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Intangible assets, Accumulated (Amortization) Accretion	$ (792,929)	$ (794,717)
Intangible assets, Net	170,810
Intangible assets, Gross	963,739	979,814	$ 983,519	$ 981,160
Intangible assets, Net	170,810	185,097
Intangible liabilities, Gross	(23,900)	(23,900)	$ (23,900)	$ (23,900)
Intangible liabilities, Accumulated (Amortization) Accretion	15,458	13,450
Intangible liabilities, Net	(8,442)	(10,450)
Core-developed technology [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	501,124	507,669
Intangible assets, Accumulated (Amortization) Accretion	(457,310)	(458,109)
Intangible assets, Net	43,814	49,560
Customer contracts and relationships [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	372,983	381,288
Intangible assets, Accumulated (Amortization) Accretion	(251,122)	(251,509)
Intangible assets, Net	121,861	129,779
Trademarks and trade names [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	77,613	78,837
Intangible assets, Accumulated (Amortization) Accretion	(73,083)	(73,732)
Intangible assets, Net	4,530	5,105
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	12,019	12,020
Intangible assets, Accumulated (Amortization) Accretion	(11,414)	(11,367)
Intangible assets, Net	$ 605	$ 653