Intangible Assets and Liabilities Gross Carrying Amount and Accumulated Amortization (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Intangible assets, Accumulated (Amortization) Accretion	$ (875,165)	$ (867,082)
Intangible assets, Net	103,763
Intangible assets, Gross	978,928	1,000,037	$ 971,648	$ 979,814
Intangible assets, Net	103,763	132,955
Intangible liabilities, Gross	(23,900)	(23,900)	$ (23,900)	$ (23,900)
Intangible liabilities, Accumulated (Amortization) Accretion	22,950	21,479
Intangible liabilities, Net	(950)	(2,421)
Core-developed technology [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	511,885	525,051
Intangible assets, Accumulated (Amortization) Accretion	(495,799)	(498,113)
Intangible assets, Net	16,086	26,938
Customer contracts and relationships [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	376,572	383,245
Intangible assets, Accumulated (Amortization) Accretion	(291,783)	(280,497)
Intangible assets, Net	84,789	102,748
Trademarks and trade names [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	78,448	79,716
Intangible assets, Accumulated (Amortization) Accretion	(75,933)	(76,912)
Intangible assets, Net	2,515	2,804
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible assets, Gross	12,023	12,025
Intangible assets, Accumulated (Amortization) Accretion	(11,650)	(11,560)
Intangible assets, Net	$ 373	$ 465