Marketable Investment Securities (Tables)

9 Months Ended

Sep. 30, 2021

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, 2021 and December 31, 2020 were as follows:


(in millions)	Amortized cost		Gross unrealized holding gains		Gross unrealized holding losses		Estimated fair value
September 30, 2021
Cash and cash equivalents:
Cash	$	208.8	$	—	$	—	$	208.8
Cash equivalents	86.4		—		—		86.4
Total cash and cash equivalents	295.2		—		—		295.2
Available-for-sale:
Corporate bonds and notes	90.7		0.2		(0.1)		90.8
Municipal bonds	19.4		0.1		—		19.5
Federal agency issues	2.6		—		—		2.6
US government securities	5.5		—		—		5.5
Total	$	413.4	$	0.3	$	(0.1)	$	413.6


(in millions)	Amortized cost		Gross unrealized holding gains		Gross unrealized holding losses		Estimated fair value
December 31, 2020:
Cash and cash equivalents:
Cash	$	47.9	$	—	$	—	$	47.9
Cash equivalents	69.1		—		—		69.1
Total cash and cash equivalents	117.0		—		—		117.0
Available-for-sale:
Corporate bonds and notes	28.8		0.5		—		29.3
Municipal bonds	9.4		0.2		—		9.6
Federal agency issues	4.0		—		—		4.0
US government securities	11.7		0.1		—		11.8
Total	$	170.9	$	0.8	$	—	$	171.7

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 securities were as follows at September 30, 2021:


(in millions)	Amortized cost		Estimated fair value
Cash	$	208.8	$	208.8
Cash equivalents	86.4		86.4
Available-for-sale:
Due within one year	70.7		70.9
Due after one year through five years	47.5		47.5
Due after five years	—		—
Total	$	413.4	$	413.6