Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2020

Investments, Debt and Equity Securities [Abstract]

Realized Gain (Loss) on Investments

The proceeds from maturities and sales of available-for-sale debt securities and resulting realized gains and losses are summarized below. In the second quarter of 2020, we liquidated all of our available-for-sale debt securities to fund the acquisition of Portola. Additionally, we liquidated all available-for-sale debt securities acquired in connection with the Portola acquisition.

	Three months ended				Nine months ended
	September 30,				September 30,
	2020		2019		2020		2019
Proceeds from maturities and sales (1)	$	25.5	$	645.4	$	1,042.4	$	2,271.7
Realized gains	$	—	$	—	$	—	$	—
Realized losses	$	—	$	—	$	—	$	—
(1) Proceeds from maturities and sales of available-for-sale debt securities include securities previously classified as cash and cash equivalents and marketable securities in the condensed consolidated balance sheet.

Schedule of Available-for-sale Securities Reconciliation

The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale debt securities by type of security as of December 31, 2019 were as follows:

	December 31, 2019
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Commercial paper	$	246.9	$	—	$	—	$	246.9
Corporate bonds	24.3		—		—		24.3
Other government-related obligations:
U.S.	70.4		—		—		70.4
Bank certificates of deposit	27.4		—		—		27.4
Total available-for-sale debt securities	$	369.0	$	—	$	—	$	369.0

Available-for-sale Securities by Balance Sheet Location Classification

The fair values of available-for-sale debt securities by classification in the condensed consolidated balance sheets were as follows:

	September 30, 2020		December 31, 2019
Cash and cash equivalents	$	—	$	328.1
Marketable securities	—		40.9
	$	—	$	369.0