Cash Equivalents and Investments - Available-For-Sale (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Available-for-sale debt securities:
Amortized Cost	$ 437.8	$ 821.1
Gross Unrealized Gains	37.4	38.2
Gross Unrealized Losses	(9.5)	(2.2)
Estimated Fair Value	465.7	857.1
Cash equivalents
Available-for-sale debt securities:
Amortized Cost	70.6	47.2
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	70.6	47.2
Short-term investments
Available-for-sale debt securities:
Amortized Cost	205.9	306.8
Gross Unrealized Gains	0.0	0.7
Gross Unrealized Losses	(3.3)	(0.1)
Estimated Fair Value	202.6	307.4
Long-term investments
Available-for-sale debt securities:
Amortized Cost	145.8	457.5
Gross Unrealized Gains	0.0	0.1
Gross Unrealized Losses	(6.2)	(2.1)
Estimated Fair Value	139.6	455.5
Other long-term assets
Available-for-sale debt securities:
Amortized Cost	15.5	9.6
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	52.9	47.0
Total fixed income securities
Available-for-sale debt securities:
Amortized Cost	422.3	811.5
Gross Unrealized Gains	0.0	0.8
Gross Unrealized Losses	(9.5)	(2.2)
Estimated Fair Value	412.8	810.1
Asset-backed and mortgage-backed securities
Available-for-sale debt securities:
Amortized Cost	37.8	139.1
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(1.2)	(0.5)
Estimated Fair Value	36.6	138.6
Certificates of deposit
Available-for-sale debt securities:
Amortized Cost	0.0	5.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	0.0	5.0
Commercial paper
Available-for-sale debt securities:
Amortized Cost	0.0	75.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	0.0	75.8
Corporate debt securities
Available-for-sale debt securities:
Amortized Cost	277.5	443.3
Gross Unrealized Gains	0.0	0.7
Gross Unrealized Losses	(7.1)	(1.5)
Estimated Fair Value	270.4	442.5
Foreign government debt securities
Available-for-sale debt securities:
Amortized Cost	8.8	12.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.4)	(0.1)
Estimated Fair Value	8.4	12.7
Time deposits
Available-for-sale debt securities:
Amortized Cost	70.6	35.2
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	70.6	35.2
U.S. government agency securities
Available-for-sale debt securities:
Amortized Cost	18.6	26.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.6)	(0.1)
Estimated Fair Value	18.0	26.7
U.S. government securities
Available-for-sale debt securities:
Amortized Cost	9.0	73.5
Gross Unrealized Gains	0.0	0.1
Gross Unrealized Losses	(0.2)	0.0
Estimated Fair Value	8.8	73.6
Privately-held debt and redeemable preferred stock securities
Available-for-sale debt securities:
Amortized Cost	15.5	9.6
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	$ 52.9	$ 47.0

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
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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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