Marketable Investment Securities (Tables)

3 Months Ended

Sep. 30, 2018

Investments Debt And Equity Securities [Abstract]

Schedule of Fair Value for Available-for-Sale Securities by Major Security Type and Class of Security

The amortized cost, gross unrealized holding gains, gross unrealized holding losses, and fair value for available-for-sale securities by major security type and class of security at September 30, 2018 and June 30, 2018 were as follows:

			Gross		Gross
			unrealized		unrealized
	Amortized		holding		holding			Estimated
	cost		gains		losses			fair value
At September 30, 2018:
Cash and cash equivalents:
Cash	$	75.3	$	—	$	—		$	75.3
Cash equivalents		18.0		—		—		$	18.0
Total cash and cash equivalents		93.3		—		—			93.3
Available-for-sale:
Corporate bonds and notes		57.5		—		(0.3	)		57.2
Municipal bonds		23.4		—		(0.1	)		23.3
Federal agency issues		9.6		—		—			9.6
US government securities		8.3		—		—			8.3
Total	$	192.1	$	—	$	(0.4	)	$	191.7

			Gross		Gross
			unrealized		unrealized
	Amortized		holding		holding			Estimated
	cost		gains		losses			fair value
At June 30, 2018:
Cash and cash equivalents:
Cash	$	95.6	$	—	$	—		$	95.6
Cash equivalents		15.3		—		—			15.3
Total cash and cash equivalents		110.9		—		—			110.9
Available-for-sale:
Corporate bonds and notes		50.8		—		(0.3	)		50.5
Municipal bonds		29.3		—		(0.1	)		29.2
Federal agency issues		12.6		—		(0.1	)		12.5
US government securities		8.3		—		(0.1	)		8.2
Total	$	211.9	$	—	$	(0.6	)	$	211.3

Schedule of Maturities of Debt Securities Classified as Cash Equivalents and Available-For-Sale Securities

Cash, cash equivalents, and maturities of debt securities classified as available-for-sale securities are as follows at September 30, 2018:

	Amortized		Estimated
	cost		fair value
Cash	$	75.3	$	75.3
Cash equivalents		18.0		18.0
Available-for-sale:
Due within one year		75.9		75.6
Due after one year through five years		22.9		22.8
Due after five years		—		—
Total	$	192.1	$	191.7