Cash, Cash Equivalents and Short-Term Investments - Contractual Maturities (Details) $ in Millions	Sep. 30, 2020 USD ($)
Amortized cost
Due within one year	$ 348.3
Due between one to three years	347.3
Due after three years	73.2
Total	768.8
Estimated fair value
Due within one year	349.2
Due between one to three years	350.9
Due after three years	73.7
Total	$ 773.8

Available For Sale Securities, Debt Maturities After Three Years, Amortized Cost

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