Investments (Tables)

12 Months Ended

Mar. 31, 2019

Investments [Abstract]

Summary of Available-for-Sale Securities

The following is a summary of available-for-sale debt securities at March 31, 2018 (in millions):

	Available-for-sale Debt Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available-for-sale debt securities:
Government agency bonds	$	723.2	$	—	$	—	$	723.2
Municipal bonds - taxable	14.9		—		—		14.9
Time deposits	11.5		—		—		11.5
Corporate bonds and debt	542.9		—		—		542.9
Total	$	1,292.5	$	—	$	—	$	1,292.5

Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Securities, by Maturity

The amortized cost and estimated fair value of the available-for-sale debt securities at March 31, 2018, by maturity are shown below (in millions). Expected maturities can differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties, and the Company views its available-for-sale debt securities as available for current operations.

	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available-for-sale
Due in one year or less	$	246.5	$	—	$	—	$	246.5
Due after one year and through five years	1,046.0		—		—		1,046.0
Due after five years and through ten years	—		—		—		—
Due after ten years	—		—		—		—
Total	$	1,292.5	$	—	$	—	$	1,292.5