Cash, cash equivalents and investments

As of September 30, 2018 and December 31, 2017, cash, cash equivalents, and investments comprised of funds in depository, money market accounts, U.S. treasury securities, asset backed securities, and corporate bonds. The following table presents the cash equivalents and investments carried at fair value in accordance with the hierarchy defined in Note 2 (in thousands):



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
September 30, 2018
Money market funds, included in cash equivalents	$	34,602	$	34,602	$	—	$	—
Investments - U.S. treasuries	2,694		2,694		—		—
Investments - Asset-backed securities	9,227		—		9,227		—
Investments - Corporate bonds	35,901		—		35,901		—
Total	$	82,424	$	37,296	$	45,128	$	—

December 31, 2017
Money market funds, included in cash equivalents	$	4,583	$	4,583	$	—	$	—
Corporate bonds, included in cash equivalents	13,595		—		13,595		—
Investments - U.S. treasuries	4,172		4,172		—		—
Investments - Asset-backed securities	6,384		—		6,384		—
Investments - Corporate bonds	34,117		—		34,117		—
Total	$	62,851	$	8,755	$	54,096	$	—

Cash equivalents and marketable securities have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market-based approaches and observable market inputs to determine value. The Company validates the prices provided by its third-party pricing services by reviewing their pricing methods and obtaining market values from other pricing sources, as needed. After completing its validation procedures, the Company did not adjust any fair value measurements provided by the pricing services as of September 30, 2018.

Cash equivalents and investments at September 30, 2018 consist of the following (in thousands):



	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses			Fair Value
Investments
U.S. treasuries	46-67	$	2,702	$	—	$	(8	)	$	2,694
Asset-backed securities	15-319	9,228		7		(8		)	9,227
Corporate bonds	1-207	35,615		319		(33		)	35,901
Total		$	47,545	$	326	$	(49	)	$	47,822

The Company recorded $0.8 million and $0.7 million of realized gains from the maturity of available-for-sale securities during the three and nine months ended September 30, 2018, respectively. No realized gains or losses were recognized during the three and nine months ended September 30, 2017, respectively.