CASH AND INVESTMENTS

Cash, Cash Equivalents and Restricted Cash

A reconciliation of Cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheets to the amount reported within the Condensed Consolidated Statements of Cash Flows was as follows (in thousands):



	March 31, 2018		December 31, 2017		March 31, 2017		December 31, 2016
Cash and cash equivalents	$	232,331	$	183,164	$	183,179	$	151,686
Restricted cash included in short-term restricted cash and investments	504		504		—		—
Restricted cash included in long-term restricted cash and investments	1,500		4,646		4,150		4,150
Cash, cash equivalents, and restricted cash as reported within the Condensed Consolidated Statements of Cash Flows	$	234,335	$	188,314	$	187,329	$	155,836

Restricted cash includes certificates of deposit used to collateralize letters of credit and, in prior periods, a purchasing card program. See “Note 11. Commitments” for a description of the collateral requirements for our letters of credit and the purchasing card program.

Investments Available-for-sale

Investments by security type were as follows; the amounts presented exclude cash, but include investments classified as cash equivalents (in thousands):



	March 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Money market funds	$	55,241	$	—	$	—		$	55,241
Commercial paper	237,067		—		—			237,067
Corporate bonds	191,361		13		(843		)	190,531
U.S. Treasury and government sponsored enterprises	21,490		—		(57		)	21,433
Total	$	505,159	$	13	$	(900	)	$	504,272



	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Money market funds	$	45,478	$	—	$	—		$	45,478
Commercial paper	199,647		—		—			199,647
Corporate bonds	179,336		18		(332		)	179,022
U.S. Treasury and government sponsored enterprises	16,295		—		(32		)	16,263
Total	$	440,756	$	18	$	(364	)	$	440,410

Gains and losses on the sales of investments available-for-sale were nominal during both the three months ended March 31, 2018 and 2017.

The fair value of and gross unrealized losses on investments available-for-sale in an unrealized loss position were as follows (in thousands):



	March 31, 2018
	In an Unrealized Loss Position Less than 12 Months					In an Unrealized Loss Position 12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate bonds	$	167,459	$	(822	)	$	9,077	$	(21	)	$	176,536	$	(843	)
U.S. Treasury and government sponsored enterprises	17,000		(52		)	2,655		(5		)	19,655		(57		)
Total	$	184,459	$	(874	)	$	11,732	$	(26	)	$	196,191	$	(900	)



	December 31, 2017
	In an Unrealized Loss Position Less than 12 Months					In an Unrealized Loss Position 12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate bonds	$	140,746	$	(296	)	$	20,047	$	(36	)	$	160,793	$	(332	)
U.S. Treasury and government sponsored enterprises	13,611		(23		)	2,651		(9		)	16,262		(32		)
Total	$	154,357	$	(319	)	$	22,698	$	(45	)	$	177,055	$	(364	)

There were 150 and 134 investments in an unrealized loss position as of March 31, 2018 and December 31, 2017, respectively. During the three months ended March 31, 2018 and 2017 we did not record any other-than-temporary impairment charges on our available-for-sale securities. Based upon our quarterly impairment review, we determined that the unrealized losses were not attributed to credit risk, but were primarily associated with changes in interest rates. Based on the scheduled maturities of our investments and our determination that it was more likely than not that we will hold these investments for a period of time sufficient for a recovery of our cost basis, we concluded that the unrealized losses in our investment securities were not other-than-temporary.

The fair value of cash equivalents and investments by contractual maturity were as follows (in thousands):



	December 31,
	2018		2017
Maturing in one year or less	$	410,062	$	377,155
Maturing after one year through five years	94,210		63,255
Total	$	504,272	$	440,410