Cash, Cash Equivalents and Investments

As of December 31, 2018 and 2017, cash, cash equivalents and investment comprised funds in depository, money market accounts, US 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 at December 31, 2018 and 2017 (in thousands):



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2018
Money market funds, included in cash equivalents	$	7,791	$	7,791	$	—	$	—
Corporate bonds, included in cash equivalents	10,910		—		10,910		—
Investments - US treasuries	7,518		7,518		—		—
Investments - Asset-backed securities	5,758		—		5,758		—
Investments - Corporate bonds	39,964		—		39,964		—
Total	$	71,941	$	15,309	$	56,632	$	—



	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
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 - US 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 December 31, 2018.

Investments at December 31, 2018 consist of the following (in thousands):



	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses			Fair Value
Investments
US treasuries	150-164	$	7,541	$	—	$	(23	)	$	7,518
Asset-backed securities	196-259	5,766		1		(9		)	5,758
Corporate bonds	73-252	40,072		3		(111		)	39,964
Total		$	53,379	$	4	$	(143	)	$	53,240

Investments at December 31, 2017 consist of the following (in thousands):



	Contractual maturity (in days)	Amortized Cost		Unrealized gains		Unrealized losses			Fair Value
Investments
US treasuries	212-340	$	4,287	$	—	$	(115	)	$	4,172
Asset-backed securities	197-365	2,709		—		(14		)	2,695
Asset-backed securities	greater than 365	3,798		—		(110		)	3,688
Corporate bonds	91-365	28,356		—		(473		)	27,882
Corporate bonds	greater than 365	6,344		1		(108		)	6,236
Total		$	45,494	$	1	$	(820	)	$	44,673

There were $1.0 million of realized gains for the year ended December 31, 2018. No realized gains or losses were recorded for the year ended December 31, 2017.