3. Amortized Cost and Fair Value of Debt Securities (Details) $ in Millions	Sep. 30, 2020 USD ($)
Fair Value Disclosures [Abstract]
Mature in less than one year	$ 95.0
Mature in one to five years	113.5
Mature in more than five years	46.7
Total Amortized Cost	255.2
Mature in less than one year	95.7
Mature in one to five years	116.4
Mature in more than five years	49.2
Estimated Fair Value	$ 261.3

Amortized cost of 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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