Investments - Schedule of Marketable Securities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Available for Sale Debt Securities
Amortized cost	$ 44.4	$ 47.3
Fair value	45.6	48.3
U.S. treasury and government agencies
Available for Sale Debt Securities
Amortized cost	13.7	16.5
Asset-backed securities
Available for Sale Debt Securities
Amortized cost	0.0	0.1
Corporate debt securities
Available for Sale Debt Securities
Amortized cost	20.3	15.1
State and municipal bonds
Available for Sale Debt Securities
Amortized cost	10.4	11.6
Other U.S. and non-U.S. government bonds
Available for Sale Debt Securities
Amortized cost	0.0	4.0
Current Asset \| U.S. treasury and government agencies
Available for Sale Debt Securities
Fair value	13.8	17.0
Current Asset \| Asset-backed securities
Available for Sale Debt Securities
Fair value	0.0	0.1
Current Asset \| Corporate debt securities
Available for Sale Debt Securities
Fair value	21.1	15.4
Current Asset \| State and municipal bonds
Available for Sale Debt Securities
Fair value	10.7	11.8
Current Asset \| Other U.S. and non-U.S. government bonds
Available for Sale Debt Securities
Fair value	$ 0.0	$ 4.0
Minimum \| U.S. treasury and government agencies
Available for Sale Debt Securities
Maturity date	Mar. 31, 2021
Minimum \| Corporate debt securities
Available for Sale Debt Securities
Maturity date	Aug. 15, 2021
Minimum \| State and municipal bonds
Available for Sale Debt Securities
Maturity date	Feb. 01, 2022
Maximum \| U.S. treasury and government agencies
Available for Sale Debt Securities
Maturity date	Jul. 21, 2028
Maximum \| Corporate debt securities
Available for Sale Debt Securities
Maturity date	Sep. 15, 2027
Maximum \| State and municipal bonds
Available for Sale Debt Securities
Maturity date	Mar. 01, 2026

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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