Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2020

Investments, Debt and Equity Securities [Abstract]

Summary of financial assets with maturities of less than 90 days included within cash and cash equivalents

The following table summarizes our financial assets with maturities of less than 90 days from the date of purchase included in cash and cash equivalents in our condensed consolidated balance sheets:

(In millions)	As of June 30, 2020		As of December 31, 2019
Commercial paper	$	139.9	$	384.4
Overnight reverse repurchase agreements	247.7		368.8
Money market funds	1,363.7		1,628.5
Short-term debt securities	118.3		159.4
Total	$	1,869.6	$	2,541.1

Marketable debt and equity securities

The following tables summarize our marketable debt and equity securities:

As of June 30, 2020 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities:
Current	$	1,282.5	$	1.5	$	(0.1	)	$	1,283.9
Non-current	502.8		3.8		(0.3		)	506.3
Government securities:
Current	657.7		0.5		—			658.2
Non-current	307.9		0.8		(0.1		)	308.6
Mortgage and other asset backed securities:
Current	0.6		—		—			0.6
Non-current	107.6		0.7		(0.4		)	107.9
Total marketable debt securities	$	2,859.1	$	7.3	$	(0.9	)	$	2,865.5
Marketable equity securities, non-current	$	428.0	$	114.6	$	(15.6	)	$	527.0

As of December 31, 2019 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities:
Current	$	1,057.2	$	1.0	$	—		$	1,058.2
Non-current	633.9		3.0		—			636.9
Government securities:
Current	502.9		0.4		—			503.3
Non-current	510.1		0.8		(0.3		)	510.6
Mortgage and other asset backed securities:
Current	0.7		—		—			0.7
Non-current	260.2		0.8		(0.4		)	260.6
Total marketable debt securities	$	2,965.0	$	6.0	$	(0.7	)	$	2,970.3
Marketable equity securities, non-current	$	218.4	$	132.1	$	(13.0	)	$	337.5

Summary of contractual maturities: available-for-sale securities

The estimated fair value and amortized cost of our marketable debt securities available-for-sale by contractual maturity are summarized as follows:

	As of June 30, 2020				As of December 31, 2019
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	1,942.7	$	1,940.8	$	1,562.2	$	1,560.8
Due after one year through five years	862.6		858.5		1,234.5		1,230.4
Due after five years	60.2		59.8		173.6		173.8
Total marketable debt securities	$	2,865.5	$	2,859.1	$	2,970.3	$	2,965.0

Proceeds from marketable debt securities

The proceeds from maturities and sales of marketable debt securities and resulting realized gains and losses are summarized as follows:

	For the Three Months Ended June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Proceeds from maturities and sales	$	1,490.6		$	1,766.6		$	3,879.9		$	3,255.8
Realized gains	6.1			1.0			11.8			1.6
Realized losses	(5.2		)	(0.3		)	(24.3		)	(0.6		)