3. Amortized Cost and Fair Value of Debt Securities (Details) $ in Millions	Jun. 30, 2020 USD ($)
Fair Value Disclosures [Abstract]
Mature in less than one year	$ 187.8
Mature in one to five years	128.6
Mature in more than five years	52.7
Total Amortized Cost	369.1
Mature in less than one year	188.7
Mature in one to five years	131.5
Mature in more than five years	55.3
Estimated Fair Value	$ 375.5

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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