Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2019

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 March 31, 2019		As of December 31, 2018
Commercial paper	$	446.0	$	231.2
Overnight reverse repurchase agreements	192.7		—
Money market funds	1,074.4		279.5
Short-term debt securities	168.8		194.8
Total	$	1,881.9	$	705.5

Marketable debt and equity securities

The following tables summarize our marketable debt and equity securities:



As of March 31, 2019 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities
Current	$	981.0	$	0.5	$	(0.1	)	$	981.4
Non-current	852.0		2.8		(0.5		)	854.3
Government securities
Current	683.6		0.2		(0.1		)	683.7
Non-current	237.5		0.3		(0.2		)	237.6
Mortgage and other asset backed securities
Current	0.7		—		—			0.7
Non-current	280.3		0.8		(0.3		)	280.8
Total marketable debt securities	$	3,035.1	$	4.6	$	(1.2	)	$	3,038.5
Marketable equity securities, non-current	489.3		421.7		(7.0		)	904.0



As of December 31, 2018 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities
Current	$	1,608.4	$	—	$	(0.9	)	$	1,607.5
Non-current	854.9		0.7		(3.9		)	851.7
Government securities
Current	706.1		0.1		(0.4		)	705.8
Non-current	264.0		0.1		(0.3		)	263.8
Mortgage and other asset backed securities
Current	0.1		—		—			0.1
Non-current	260.5		0.4		(0.5		)	260.4
Total marketable debt securities	$	3,694.0	$	1.3	$	(6.0	)	$	3,689.3
Marketable equity securities, non-current	496.2		127.7		(8.5		)	615.4

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 March 31, 2019				As of December 31, 2018
(In millions)	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	1,665.3	$	1,665.8	$	2,314.6	$	2,313.4
Due after one year through five years	1,234.8		1,237.8		1,235.9		1,232.7
Due after five years	135.0		134.9		143.5		143.2
Total available-for-sale securities	$	3,035.1	$	3,038.5	$	3,694.0	$	3,689.3

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 March 31,
(In millions)	2019			2018
Proceeds from maturities and sales	$	1,489.2		$	4,068.9
Realized gains	$	0.6		$	1.8
Realized losses	$	(0.3	)	$	(9.4	)