Goodwill and Purchased Intangible Assets - Purchased Intangible Assets, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Purchased Intangible Assets [Line Items]
Gross	$ 835,600,000	$ 733,700,000
Accumulated amortization	(646,100,000)	(611,500,000)
Impairment and other charges	(52,700,000)	(52,700,000)
Net	136,800,000	69,500,000
Total purchased intangible assets, gross	884,600,000	782,700,000
Purchased intangible assets, net	185,800,000	118,500,000
Amortization of intangible assets	34,700,000	17,400,000	$ 17,500,000
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	729,100,000	648,100,000
Accumulated amortization	(564,000,000.0)	(534,000,000.0)
Impairment and other charges	(49,900,000)	(49,900,000)
Net	115,200,000	64,200,000
Customer contracts, support agreements, and related relationships
Purchased Intangible Assets [Line Items]
Gross	98,600,000	83,600,000
Accumulated amortization	(79,300,000)	(75,500,000)
Impairment and other charges	(2,800,000)	(2,800,000)
Net	16,500,000	5,300,000
Trade name
Purchased Intangible Assets [Line Items]
Gross	7,900,000	2,000,000.0
Accumulated amortization	(2,800,000)	(2,000,000.0)
Impairment and other charges	0	0
Net	$ 5,100,000	$ 0