Investments (Tables) - Available-for-Sale Investments

3 Months Ended

Mar. 31, 2019

Investments

Schedule of marketable investments classified as available-for-sale

Marketable investments classified as available-for-sale consisted of the following (in millions):

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
As of March 31, 2019	Cost		Gains		Losses		Value
U.S. government and agency securities	$	1,111.8	$	1.3	$	(2.0)	$	1,111.1
Corporate debt securities		111.2		0.5		—		111.7
Total	$	1,223.0	$	1.8	$	(2.0)	$	1,222.8
Reported under the following captions on the consolidated balance sheet:
Cash and cash equivalents							$	5.9
Current marketable investments								806.4
Non-current marketable investments								410.5
Total							$	1,222.8

			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 the consolidated balance sheet:
Cash and cash equivalents							$	—
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 March 31, 2019
	Amortized		Fair
	Cost		Value
Due within one year	$	813.4	$	812.3
Due in one to three years		409.6		410.5
Total	$	1,223.0	$	1,222.8

	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