2. Cash, Cash Equivalents, Restricted Cash and Short-Term Investments

The following table provides a summary of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheets that reconciles to the corresponding amount in the Condensed Consolidated Statements of Cash Flows (in thousands):

	As of March 31, 2018		As of December 31, 2017		As of March 31, 2017		As of December 31, 2016
Cash and cash equivalents	$	214,274	$	192,538	$	136,318	$	107,343
Restricted cash included in Current assets		51		52		72		68
Restricted cash included in Non-current assets		2,332		2,284		1,898		1,884
Total cash, cash equivalents, and restricted cash shown in the Statements of Cash Flows	$	216,657	$	194,874	$	138,288	$	109,295

The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand, highly liquid investments in commercial paper, money market funds, corporate debt obligations and various deposit accounts. Restricted cash represents bank deposits to secure bank guarantees provided to its lessors for its operating lease arrangements.

The Company considers all high quality investments purchased with original maturities at the date of purchase greater than three months to be short-term investments. Investments are available to be used for current operations and are, therefore, classified as current assets even though maturities may extend beyond one year. Cash equivalents and short-term investments are classified as available-for-sale and are, therefore, recorded at fair value on the condensed consolidated balance sheets, with any unrealized gains and losses reported in accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in its condensed consolidated balance sheets, until realized. The Company uses the specific-identification method to compute gains and losses on the investments. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included as a component of other income (expense), net in the condensed consolidated statements of operations.

Cash, cash equivalents and short-term investments consist of the following (in thousands):

	As of March 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash and cash equivalents:
Cash	$	110,746		-		-	$	110,746
Commercial paper		3,995		-		2		3,993
Money market funds		84,081		-		-		84,081
US government and US government agencies		15,455		-		1		15,454
Total	$	214,277		-	$	3	$	214,274
Short-term investments:
Commercial paper		-		-		-		-
Corporate debt obligations		118,628		-		799		117,829
US government and US government agencies		46,426		-		199		46,227
Bank deposits		480		-		1		479
Total	$	165,534		-	$	999	$	164,535

	As of December 31, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Cash and cash equivalents:
Cash	$	92,030		-		-	$	92,030
Commercial paper		-		-		-		-
Money market funds		84,144		-		-		84,144
US government and US government agencies		16,367		-		3		16,364
Total	$	192,541		-	$	3	$	192,538
Short-term investments:
Commercial paper	$	699		-		-	$	699
Corporate debt obligations		123,320		-		488		122,832
US government and US government agencies		43,097		-		114		42,983
Bank deposits		480		-		1		479
Total	$	167,596		-	$	603	$	166,993

The following table summarizes the cost and estimated fair value of short-term investments based on stated effective maturities as of March 31, 2018 (in thousands):

	As of March 31, 2018
			Estimated
	Amortized		Fair
	Cost		Value
Short-term investments:
Due within one year	$	110,202	$	109,734
Due within two years		55,332		54,801
Total	$	165,534	$	164,535

The gross unrealized loss related to these securities was due primarily to changes in interest rates. The Company reviews its short-term investments on a regular basis to evaluate whether or not any security has experienced an other-than-temporary decline in fair value. The Company considers factors such as the length of time and extent to which the market value has been less than the cost, the financial condition and near-term prospects of the issuer and its intent to sell, or whether it is more likely than not the Company will be required to sell, the investment before recovery of the investment’s amortized cost basis. If the Company believes that an other-than-temporary decline exists in one of these securities, the Company will write down these investments to fair value. For debt securities, the portion of the write-down related to credit loss would be recorded to other income (expense), net, in the Company’s condensed consolidated statements of operations. Any portion not related to credit loss would be recorded to accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in the Company’s condensed consolidated balance sheets. During the three months ended March 31, 2018 and 2017, the Company did not consider any of its investments to be other-than-temporarily impaired.

The following tables show the short-term investments in an unrealized loss position and the related gross unrealized losses and fair value and length of time that the short-term investments have been in a continuous unrealized loss position (in thousands):

	As of March 31, 2018
	Less than 12 Months				12 Months or Greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper					$	-	$	-	$	-	$	-
Corporate debt obligations		47,967		492		69,863		307		117,830		799
US government and US government agencies		34,753		173		11,473		26		46,226		199
Bank deposits						479		1		479		1
	$	82,720	$	665	$	81,815	$	334	$	164,535	$	999

	As of December 31, 2017
	Less than 12 Months				12 Months or Greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	699	$	-	$	-	$	-	$	699	$	-
Corporate debt obligations		77,715		377		45,117		111		122,832		488
US government and US government agencies		29,093		76		11,461		38		40,554		114
Bank deposits		-		-		479		1		479		1
	$	107,507	$	453	$	57,057	$	150	$	164,564	$	603