Cash Equivalents and Investments - Available-For-Sale (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Available-for-sale debt securities:
Amortized Cost	$ 378.2	$ 437.8
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	(6.8)	(9.5)
Estimated Fair Value	408.8	465.7
Cash equivalents
Available-for-sale debt securities:
Amortized Cost	89.7	70.6
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	89.7	70.6
Short-term investments
Available-for-sale debt securities:
Amortized Cost	171.4	205.9
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(3.0)	(3.3)
Estimated Fair Value	168.4	202.6
Long-term investments
Available-for-sale debt securities:
Amortized Cost	96.4	145.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(3.8)	(6.2)
Estimated Fair Value	92.6	139.6
Other long-term assets
Available-for-sale debt securities:
Amortized Cost	20.7	15.5
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	58.1	52.9
Total fixed income securities
Available-for-sale debt securities:
Amortized Cost	357.5	422.3
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(6.8)	(9.5)
Estimated Fair Value	350.7	412.8
Asset-backed and mortgage-backed securities
Available-for-sale debt securities:
Amortized Cost	24.6	37.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.8)	(1.2)
Estimated Fair Value	23.8	36.6
Corporate debt securities
Available-for-sale debt securities:
Amortized Cost	210.8	277.5
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(5.2)	(7.1)
Estimated Fair Value	205.6	270.4
Foreign government debt securities
Available-for-sale debt securities:
Amortized Cost	8.8	8.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.3)	(0.4)
Estimated Fair Value	8.5	8.4
Time deposits
Available-for-sale debt securities:
Amortized Cost	89.7	70.6
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	89.7	70.6
U.S. government agency securities
Available-for-sale debt securities:
Amortized Cost	18.6	18.6
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.4)	(0.6)
Estimated Fair Value	18.2	18.0
U.S. government securities
Available-for-sale debt securities:
Amortized Cost	5.0	9.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.1)	(0.2)
Estimated Fair Value	4.9	8.8
Privately-held debt and redeemable preferred stock securities
Available-for-sale debt securities:
Amortized Cost	20.7	15.5
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	$ 58.1	$ 52.9

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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