Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2017

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 on the accompanying condensed consolidated balance sheets:

(In millions)	As of March 31, 2017		As of December 31, 2016
Commercial paper	$	71.9	$	31.0
Money market funds	519.2		741.7
Short-term debt securities	54.0		1,266.9
Total	$	645.1	$	2,039.6

Marketable debt and equity securities

The following tables summarize our marketable debt and equity securities, classified as available-for-sale:

As of March 31, 2017 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Corporate debt securities
Current	$	1,288.5	$	0.1	$	(0.8	)	$	1,289.2
Non-current	1,212.2		2.1		(3.3		)	1,213.4
Government securities
Current	664.4		0.2		(0.4		)	664.6
Non-current	1,073.8		0.8		(3.0		)	1,076.0
Mortgage and other asset backed securities
Current	3.3		—		—			3.3
Non-current	539.2		1.1		(1.4		)	539.5
Total marketable debt securities	$	4,781.4	$	4.3	$	(8.9	)	$	4,786.0
Marketable equity securities, non-current	$	18.7	$	—	$	(14.9	)	$	33.6

As of December 31, 2016 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Corporate debt securities
Current	$	1,408.6	$	0.2	$	(0.6	)	$	1,409.0
Non-current	1,255.2		1.2		(4.7		)	1,258.7
Government securities
Current	1,156.0		0.2		(0.3		)	1,156.1
Non-current	1,016.5		0.5		(3.4		)	1,019.4
Mortgage and other asset backed securities
Current	4.0		—		—			4.0
Non-current	557.7		0.8		(2.2		)	559.1
Total marketable debt securities	$	5,398.0	$	2.9	$	(11.2	)	$	5,406.3
Marketable equity securities, non-current	$	24.9	$	0.7	$	(9.3	)	$	33.5

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 March 31, 2017				As of December 31, 2016
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	1,956.2	$	1,957.1	$	2,568.6	$	2,569.1
Due after one year through five years	2,561.9		2,565.4		2,552.6		2,559.7
Due after five years	263.3		263.5		276.8		277.5
Total available-for-sale securities	$	4,781.4	$	4,786.0	$	5,398.0	$	5,406.3

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)	2017			2016
Proceeds from maturities and sales	$	1,884.3		$	1,181.1
Realized gains	$	1.2		$	0.4
Realized losses	$	(1.9	)	$	(0.4	)