CASH AND INVESTMENTS

All of our cash equivalents and investments are classified as available-for-sale. The following tables summarize cash and cash equivalents, investments, and restricted cash and investments by balance sheet line item as of June 30, 2017 and December 31, 2016 (in thousands):



	June 30, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash and cash equivalents	$	135,212	$	—	$	—		$	135,212
Short-term investments	214,172		15		(143		)	214,044
Long-term investments	26,404		26		(17		)	26,413
Long-term restricted cash and investments	4,650		—		—			4,650
Total cash and investments	$	380,438	$	41	$	(160	)	$	380,319



	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash and cash equivalents	$	151,686	$	—	$	—		$	151,686
Short-term investments	268,234		13		(130		)	268,117
Long-term investments	55,792		1		(192		)	55,601
Long-term restricted cash and investments	4,150		—		—			4,150
Total cash and investments	$	479,862	$	14	$	(322	)	$	479,554

Under our loan and security agreement with Silicon Valley Bank, we were required to maintain compensating balances on deposit in one or more investment accounts with Silicon Valley Bank or one of its affiliates. The total collateral balance of $81.6 million as of December 31, 2016 is reflected in our Condensed Consolidated Balance Sheet in short-term investments; as a result of our repayment of the term loan with Silicon Valley Bank, the compensating balance requirement was terminated as of March 29, 2017. See “Note 7 - Debt” to our Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2016 filed with the SEC on February 27, 2017 for more information regarding the collateral balance requirements under our Silicon Valley Bank loan and security agreement.

The following tables summarize our cash equivalents and investments by security type as of June 30, 2017 and December 31, 2016. The amounts presented exclude cash, but include investments classified as cash equivalents (in thousands):



	June 30, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Money market funds	$	48,253	$	—	$	—		$	48,253
Commercial paper	303,877		41		(132		)	303,786
Corporate bonds	550		—		—			550
U.S. Treasury and government sponsored enterprises	15,664		—		(28		)	15,636
Total investments	$	368,344	$	41	$	(160	)	$	368,225



	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Money market funds	$	71,457	$	—	$	—		$	71,457
Commercial paper	165,375		—		—			165,375
Corporate bonds	152,712		3		(308		)	152,407
U.S. Treasury and government sponsored enterprises	70,730		11		(14		)	70,727
Total investments	$	460,274	$	14	$	(322	)	$	459,966

Gains and losses on the sales of investments available-for-sale were nominal or zero during the three and six months ended June 30, 2017 and 2016.

All of our investments are subject to a quarterly impairment review. During the six months ended June 30, 2017 and 2016 we did not record any other-than-temporary impairment charges on our available-for-sale securities. As of June 30, 2017, there were 75 investments in an unrealized loss position with gross unrealized losses of $0.2 million and an aggregate fair value of $133.2 million. The investments in an unrealized loss position comprise corporate bonds with an aggregate fair value of $117.5 million and securities issued by U.S. Treasury and government sponsored enterprises with an aggregate fair value of $15.7 million. The unrealized losses were not attributed to credit risk, but rather associated with the changes in interest rates. Based on the scheduled maturities of our investments, we concluded that the unrealized losses in our investment securities are not other-than-temporary, as it is more likely than not that we will hold these investments for a period of time sufficient for a recovery of our cost basis.

The following table summarizes the fair value of securities classified as available-for-sale by contractual maturity as of June 30, 2017 (in thousands):



	Mature within One Year		After One Year through Two Years		Fair Value
Money market funds	$	48,253	$	—	$	48,253
Commercial paper	281,572		22,214		303,786
Corporate bonds	—		550		550
U.S. Treasury and government sponsored enterprises	13,986		1,650		15,636
Total investments	$	343,811	$	24,414	$	368,225

Cash is excluded from the table above. The classification of certain restricted investments is dependent upon the term of the underlying restriction on the asset and not the maturity date of the investment. Therefore, certain long-term restricted cash and investments have contractual maturities within one year.