Intangible Assets and Liabilities Gross Carrying Amount and Accumulated Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Intangible assets, Accumulated (Amortization) Accretion	$ (860,772)	$ (867,082)
Intangible assets, Net	122,861
Intangible assets, Gross	983,633	1,000,037	$ 963,739	$ 979,814
Intangible assets, Net	122,861	132,955
Intangible liabilities, Gross	(23,900)	(23,900)	$ (23,900)	$ (23,900)
Intangible liabilities, Accumulated (Amortization) Accretion	21,969	21,479
Intangible liabilities, Net	(1,931)	(2,421)
Core-developed technology [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	514,416	525,051
Intangible assets, Accumulated (Amortization) Accretion	(491,146)	(498,113)
Intangible assets, Net	23,270	26,938
Customer contracts and relationships [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	378,430	383,245
Intangible assets, Accumulated (Amortization) Accretion	(281,965)	(280,497)
Intangible assets, Net	96,465	102,748
Trademarks and trade names [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	78,763	79,716
Intangible assets, Accumulated (Amortization) Accretion	(76,055)	(76,912)
Intangible assets, Net	2,708	2,804
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	12,024	12,025
Intangible assets, Accumulated (Amortization) Accretion	(11,606)	(11,560)
Intangible assets, Net	$ 418	$ 465