Investments and Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Investments And Fair Value Measurements [Abstract]

Summary of Investments

The following is a summary of our investments at March 31, 2019 and December 31, 2018 (in thousands):

			Gross Unrealized					Estimated
March 31, 2019	Cost		Gains		Losses			Fair Value
Available-for-sale securities:
Corporate debt securities	$	54,414	$	4	$	(14	)	$	54,404
Debt securities issued by U.S. government agencies		58,371		23		(2	)		58,392
Total securities with a maturity of one year or less	$	112,785	$	27	$	(16	)	$	112,796
Debt securities issued by U.S. government agencies		7,961		8		—			7,969
Total securities with a maturity of one to two years		7,961		8		—			7,969
Total available-for-sale securities	$	120,746	$	35	$	(16	)	$	120,765

			Gross Unrealized					Estimated
December 31, 2018	Cost		Gains		Losses			Fair Value
Available-for-sale securities:
Corporate debt securities	$	81,770	$	—	$	(151	)	$	81,619
Debt securities issued by U.S. government agencies		85,578		—		(42	)		85,536
Total securities with a maturity of one year or less	$	167,348	$	—	$	(193	)	$	167,155

Assets Measured at Fair Value on a Recurring Basis

The following tables present the investments we held at March 31, 2019 and December 31, 2018 that are regularly measured and carried at fair value. The table segregates each security by the level within the fair value hierarchy of the valuation techniques we utilized to determine the respective securities' fair value (in thousands):

	At March 31, 2019		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)
Money market funds (1)	$	74,541	$	74,541	$	—
Corporate debt securities		54,404		—		54,404
Debt securities issued by U.S. government agencies (3)		66,361		—		66,361
Total	$	195,306	$	74,541	$	120,765

	At December 31, 2018		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)
Money market funds (1)	$	82,343	$	82,343	$	—
Corporate debt securities (2)		81,619		—		81,619
Debt securities issued by U.S. government agencies (3)		85,536		—		85,536
Total	$	249,498	$	82,343	$	167,155

(1) Included in cash and cash equivalents on our condensed consolidated balance sheets.

(2) At December 31, 2018, $1.0 million was included in cash and cash equivalents on our condensed consolidated balance sheet, with the difference included in short-term investments on our condensed consolidated balance sheet.

(3) Included in short-term investments on our condensed consolidated balance sheets.