Cash and Cash Equivalents, Short-term Investments and Restricted Cash (Tables)

9 Months Ended

Sep. 30, 2020

Cash and Cash Equivalents [Abstract]

Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Market Value of Cash and Cash Equivalents and Available-for-Sale Investments

The following tables present the amortized cost, gross unrealized gains and losses and estimated fair market value of our cash and cash equivalents, available-for-sale investments and restricted cash as of the dates presented (in thousands):

	September 30, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Market Value
Cash	$	150,556	$	—	$	—	$	150,556
Cash equivalents:
Money market funds	1,747,818		—		—		1,747,818
Treasury bills	5,000		—		—		5,000
U.S. government agency securities	1,162		—		—		1,162
Certificates of deposit	249		—		—		249
Short-term investments:
Treasury bills	1,360,011		76		(3)		1,360,084
U.S. government agency securities	499,494		514		(17)		499,991
Corporate notes and bonds	15,611		24		—		15,635
Municipal securities	8,676		3		—		8,679
Certificates of deposit	996		—		—		996
Restricted cash	44,103		—		—		44,103
Total	$	3,833,676	$	617	$	(20)	$	3,834,273

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Market Value
Cash	$	194,955	$	—	$	—	$	194,955
Cash equivalents:
Money market funds	872,431		—		—		872,431
U.S. government agency securities	35,011		—		(2)		35,009
Commercial paper	31,113		—		—		31,113
Treasury bills	6,441		—		—		6,441
Corporate notes and bonds	1,065		—		—		1,065
Certificates of deposit	249		—		—		249
Short-term investments:
U.S. government agency securities	861,862		365		(73)		862,154
Corporate notes and bonds	159,382		91		(42)		159,431
Commercial paper	150,267		—		—		150,267
Treasury bills	79,989		14		—		80,003
Municipal securities	27,836		56		(3)		27,889
Certificates of deposit	1,245		—		—		1,245
Restricted cash	89,646		—		—		89,646
Total	$	2,511,492	$	526	$	(120)	$	2,511,898