Cash, Cash Equivalents, And Available-For-Sale Securities (Tables)

6 Months Ended

Jun. 30, 2018

CASH, CASH EQUIVALENTS, AND AVAILABLE-FOR-SALE SECURITIES

Schedule of fair value and amortized cost of cash, cash equivalents, and available-for-sale securities by major security type

	As of June 30, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Estimated
Cash and cash equivalents and available-for-sale securities	Cost		Gains		Losses		Fair Value
Cash and money market funds	$	57,181	$	—	$	—	$	57,181
U.S. Treasury securities		14,513		—		(172)		14,341
Corporate debt securities		52,357		9		(346)		52,020
Total		124,051		9		(518)		123,542
Less amounts classified as cash and cash equivalents		(57,181)		—		—		(57,181)
Total available-for-sale securities	$	66,870	$	9	$	(518)	$	66,361

	As of December 31, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized		Estimated
Cash and cash equivalents and available-for-sale securities	Cost		Gains		Losses		Fair Value
Cash and money market funds	$	66,392	$	—	$	—	$	66,392
U.S. Treasury securities		21,070		1		(139)		20,932
Corporate debt securities		139,481		16		(486)		139,011
Total		226,943		17		(625)		226,335
Less amounts classified as cash and cash equivalents		(66,392)		—		—		(66,392)
Total available-for-sale securities	$	160,551	$	17	$	(625)	$	159,943

Schedule of Fair Value of Separate Accounts by Major Category of Investment

The following table represents the fair value hierarchy for our cash equivalents and available-for-sale securities by major security type (in thousands):

	As of June 30, 2018
	Level 1		Level 2		Level 3		Total
Cash and money market funds	$	57,181	$	—	$	—	$	57,181
U.S. Treasury securities		14,341		—		—		14,341
Corporate debt securities		—		52,020		—		52,020
Total	$	71,522	$	52,020	$	—	$	123,542

	As of December 31, 2017
	Level 1		Level 2		Level 3		Total
Cash and money market funds	$	66,392	$	—	$	—	$	66,392
U.S. Treasury securities		20,932		—		—		20,932
Corporate debt securities		—		139,011		—		139,011
Total	$	87,324	$	139,011	$	—	$	226,335