Marketable Investment Securities (Tables)

12 Months Ended

Dec. 31, 2022

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 debt securities classified as available-for-sale securities by major security type and class of security at December 31, 2022 and December 31, 2021 were as follows:


(in millions)	Amortized cost		Gross unrealized holding gains		Gross unrealized holding losses		Estimated fair value
December 31, 2022:
Cash and cash equivalents:
Cash	$	53.6	$	—	$	—	$	53.6
Cash equivalents	3.3		—		—		3.3
Total cash and cash equivalents	56.9		—		—		56.9
Available-for-sale:
Corporate bonds and notes	66.7		—		(1.6)		65.1
Municipal bonds	16.3		—		(0.3)		16.0
Federal agency issues	20.7		—		(0.7)		20.0
U.S. government securities	11.8		—		(0.1)		11.7
Total	$	172.4	$	—	$	(2.7)	$	169.7


(in millions)	Amortized cost		Gross unrealized holding gains		Gross unrealized holding losses		Estimated fair value
December 31, 2021:
Cash and cash equivalents:
Cash	$	194.2	$	—	$	—	$	194.2
Cash equivalents	63.2		—		—		63.2
Total cash and cash equivalents	257.4		—		—		257.4
Available-for-sale:
Corporate bonds and notes	105.7		0.1		(0.2)		105.6
Municipal bonds	16.1		—		—		16.1
Federal agency issues	6.8		—		—		6.8
U.S. government securities	11.9		—		—		11.9
Total	$	397.9	$	0.1	$	(0.2)	$	397.8

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

Cash, cash equivalents, and maturities of debt securities classified as available-for-sale are as follows at December 31, 2022:


(in millions)	Amortized cost		Estimated fair value
Cash	$	53.6	$	53.6
Cash equivalents	3.3		3.3
Available-for-sale:
Due within one year	58.8		58.0
Due after one year through five years	56.7		54.8
Due after five years	—		—
Total	$	172.4	$	169.7