Goodwill and Purchased Intangible Assets - Purchased Intangible Assets, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Purchased Intangible Assets [Line Items]
Gross	$ 962,300,000	$ 835,600,000
Accumulated Amortization	(686,700,000)	(646,100,000)
Accumulated Impairments and Other Charges	(57,900,000)	(52,700,000)
Net	217,700,000	136,800,000
Total purchased intangible assets	1,011,300,000	884,600,000
Purchased intangible assets, net	266,700,000	185,800,000
Amortization of intangible assets	40,600,000	34,700,000	$ 17,400,000
Impairment of intangible assets	0	0	$ 0
IPR&D
Purchased Intangible Assets [Line Items]
Indefinite-lived intangible assets:	49,000,000.0	49,000,000.0
Technologies and patents
Purchased Intangible Assets [Line Items]
Gross	823,500,000	729,100,000
Accumulated Amortization	(598,200,000)	(564,000,000.0)
Accumulated Impairments and Other Charges	(55,100,000)	(49,900,000)
Net	170,200,000	115,200,000
Customer contracts, support agreements, and related relationships
Purchased Intangible Assets [Line Items]
Gross	129,200,000	98,600,000
Accumulated Amortization	(84,400,000)	(79,300,000)
Accumulated Impairments and Other Charges	(2,800,000)	(2,800,000)
Net	42,000,000.0	16,500,000
Trade name
Purchased Intangible Assets [Line Items]
Gross	9,600,000	7,900,000
Accumulated Amortization	(4,100,000)	(2,800,000)
Accumulated Impairments and Other Charges	0	0
Net	$ 5,500,000	$ 5,100,000