Marketable Investment Securities (Tables)

12 Months Ended

Jun. 30, 2019

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 June 30, 2019 and 2018 were as follows:

			Gross		Gross
			unrealized		unrealized
	Amortized		holding		holding		Estimated
	cost		gains		losses		fair value
At June 30, 2019:
Cash and cash equivalents:
Cash	$	68.7	$	—	$	—	$	68.7
Cash equivalents		24.5		—		—		24.5
Total cash and cash equivalents		93.2		—		—		93.2
Available-for-sale:
Corporate bonds and notes		64.0		0.6		—		64.6
Municipal bonds		15.3		—		—		15.3
Federal agency issues		9.0		—		—		9.0
US government securities		9.7		—		—		9.7
Total	$	191.2	$	0.6	$	—	$	191.8

			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

Cash, cash equivalents, and maturities of debt securities classified as available-for-sale are as follows at June 30, 2019:

	Amortized		Estimated
	cost		fair value
Cash		68.7		68.7
Cash equivalents		24.5		24.5
Available-for-sale:
Due within one year		46.9		47.0
Due after one year through five years		51.1		51.6
Due after five years		—		—
Total	$	191.2	$	191.8

Schedule of Debt Securities Available-For-Sale in Gross Unrealized Loss Position

Debt securities available-for-sale in a gross unrealized loss position as of June 30, 2019 and 2018 are summarized as follows:

	Less than 12 months				More than 12 months				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	value		losses		value		losses		value		losses
At June 30, 2019:
Debt securities:
Corporate bonds and notes		2.5		—		12.5		—		15.0		—
Municipal bonds		—		—		5.0		—		5.0		—
Federal agency issues		—		—		5.0		—		5.0		—
US government securities		—		—		—		—		—		—
	$	2.5	$	—	$	22.5	$	—	$	25.0	$	—

	Less than 12 months				More than 12 months				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	value		losses		value		losses		value		losses
At June 30, 2018:
Debt securities:
Corporate bonds and notes		35.6		0.2		9.8		0.1		45.4		0.3
Municipal bonds		24.6		0.1		0.5		—		25.1		0
Federal agency issues		3.0		0.1		9.5		0.1		12.5		0.2
US government securities		6.3		—		2.0		—		8.3		—
	$	69.5	$	0.4	$	21.8	$	0.2	$	91.3	$	0.6