Cash, Cash Equivalents and Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2018

Cash and Cash Equivalents [Abstract]

Schedule of Cash, Cash Equivalents and Short-Term Investments

The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of December 31, 2018 consisted of the following:



	Amortized cost		Unrealized gain		Unrealized loss			Estimated fair value

Cash	$	103.0	$	—	$	—		103.0
Cash equivalents
Money market funds	355.5		—		—			355.5
Commercial paper	27.4		—		—			27.4
U.S. Treasury securities	33.4		—		—			33.4
Total cash and cash equivalents	$	519.3	$	—	$	—		$	519.3
Short-term investments
Corporate notes and obligations	269.6		0.1		(0.5		)	269.2
U.S. Treasury securities	176.0		—		(0.1		)	175.9
Certificates of deposit	70.6		—		—			70.6
U.S. agency obligations	37.1		—		—			37.1
Commercial paper	17.2		—		—			17.2
Total short-term investments	570.5		0.1		(0.6		)	570.0
Total	$	1,089.8	$	0.1	$	(0.6	)	$	1,089.3

Contractual Maturities of Short Term Investments

The following table presents the contractual maturities of the Company’s short-term investments as of December 31, 2018:



	Amortized cost		Estimated fair value

Due within one year	$	327.6	$	327.5
Due between one to three years	242.9		242.5
Total	$	570.5	$	570.0

Short-Term Investments In Unrealized Loss Positions

As of December 31, 2018, the following short-term investments were in unrealized loss positions:



	Less than 12 months					12 months or greater				Total
	Fair value		Unrealized losses			Fair value		Unrealized losses		Fair value		Unrealized losses
Corporate notes and obligations	$	209.5	$	(0.5	)	$	—	$	—	$	209.5	$	(0.5	)
U.S. Treasury securities	127.8		(0.1		)	—		—		127.8		(0.1		)
Total	$	337.3	$	(0.6	)	$	—	$	—	$	337.3	$	(0.6	)