Marketable Investment Securities (Tables)

6 Months Ended

Dec. 31, 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 December 31, 2018 and June 30, 2018 were as follows:

			Gross		Gross
			unrealized		unrealized
	Amortized		holding		holding			Estimated
	cost		gains		losses			fair value
At December 31, 2018:
Cash and cash equivalents:
Cash	$	74.2	$	—	$	—		$	74.2
Cash equivalents		16.4		—		—		$	16.4
Total cash and cash equivalents		90.6		—		—			90.6
Available-for-sale:
Corporate bonds and notes		68.6		—		(0.2	)		68.4
Municipal bonds		17.0		—		—			17.0
Federal agency issues		12.1		—		(0.1	)		12.0
US government securities		7.3		—		—			7.3
Total	$	195.6	$	—	$	(0.3	)	$	195.3

			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 December 31, 2018:

	Amortized		Estimated
	cost		fair value
Cash	$	74.2	$	74.2
Cash equivalents		16.4		16.4
Available-for-sale:
Due within one year		75.1		74.8
Due after one year through five years		29.9		29.9
Due after five years		—		—
Total	$	195.6	$	195.3