Investments (Tables) - Available-for-Sale Debt Securities

9 Months Ended

Sep. 30, 2019

Investments

Schedule of available-for-sale debt securities

Available-for-sale debt securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income in stockholders’ equity, until realized. Available-for-sale debt securities consisted of the following (in millions):

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
As of September 30, 2019	Cost		Gains		Losses		Value
U.S. government and agency securities	$	1,287.9	$	3.2	$	(0.5)	$	1,290.6
Corporate debt securities		223.6		1.8		(0.1)		225.3
Total	$	1,511.5	$	5.0	$	(0.6)	$	1,515.9
Reported under the following captions on our consolidated balance sheet:
Current marketable investments								785.5
Non-current marketable investments								730.4
Total							$	1,515.9

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
As of December 31, 2018	Cost		Gains		Losses		Value
U.S. government and agency securities	$	1,077.4	$	0.7	$	(3.9)	$	1,074.2
Corporate debt securities		72.3		—		(0.3)		72.0
Total	$	1,149.7	$	0.7	$	(4.2)	$	1,146.2
Reported under the following captions on our consolidated balance sheet:
Current marketable investments								705.8
Non-current marketable investments								440.4
Total							$	1,146.2

Summary of the contractual maturities

The following table summarizes the contractual maturities of available-for-sale marketable investments (in millions):

	As of September 30, 2019
	Amortized		Fair
	Cost		Value
Due within one year	$	784.7	$	785.5
Due in one to three years		726.8		730.4
Total	$	1,511.5	$	1,515.9

	As of December 31, 2018
	Amortized		Fair
	Cost		Value
Due within one year	$	708.2	$	705.8
Due in one to three years		441.5		440.4
Total	$	1,149.7	$	1,146.2