Financial Instruments

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Financial Instruments

FINANCIAL INSTRUMENTS

The following is a summary of marketable securities at December 31, 2017 and December 31, 2016 (in thousands):

	December 31, 2017
	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Values
Available-for-sale securities
Corporate bonds and notes	$	45,803	$	—	$	(230	)	$	45,573
Commercial paper	2,392		—		(2		)	2,390
Treasury and agency notes and bills	6,000		—		(71		)	5,929
Certificates of deposit	8,540		—		—			8,540
Money market funds	40,413		—		—			40,413
Total available-for-sale securities	$	103,148	$	—	$	(303	)	$	102,845
Reported in:
Cash and cash equivalents								$	40,413
Short-term investments								62,432
Total marketable securities								$	102,845

	December 31, 2016
	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Values
Available-for-sale securities
Corporate bonds and notes	$	36,590	$	7	$	(95	)	$	36,502
Commercial paper	5,220		—		(4		)	5,216
Treasury and agency notes and bills	6,029		—		(57		)	5,972
Money market funds	14,146		—		—			14,146
Total available-for-sale securities	$	61,985	$	7	$	(156	)	$	61,836
Reported in:
Cash and cash equivalents								$	14,457
Short-term investments								47,379
Total marketable securities								$	61,836

At December 31, 2017 and December 31, 2016, the Company had $200.7 million and $113.0 million, respectively, in cash, cash equivalents and short-term investments. A significant portion of these amounts was held in marketable securities, as shown above. The remaining balance of $97.8 million and $51.2 million at December 31, 2017 and December 31, 2016, respectively, was cash held in operating accounts not included in the tables above.

The gross realized gains and losses on sales of marketable securities were not significant during the years ended December 31, 2017, 2016 and 2015.

Unrealized losses (net of unrealized gains) of $0.3 million, net of tax, as of December 31, 2017, were related to a temporary decrease in value of the remaining available-for-sale securities and were due primarily to changes in interest rates and market and credit conditions of the underlying securities. Certain investments with a temporary decline in value are not considered to be other-than-temporarily impaired as of December 31, 2017 because the Company has the ability to hold these investments to allow for recovery, and does not anticipate having to sell these securities with unrealized losses and continues to receive interest at the maximum contractual rate. For the years ended December 31, 2017, 2016 and 2015, respectively, the Company did not record any impairment charges related to its marketable securities.

The following table summarizes the fair value and gross unrealized losses related to individual available-for-sale securities at December 31, 2017 and 2016, which have been in a continuous unrealized loss position, aggregated by investment category and length of time (in thousands):

December 31, 2017	Less Than 12 Months					12 Months or More					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate bonds and notes	$	30,811	$	(189	)	$	14,762	$	(41	)	$	45,573	$	(230	)
Treasury and agency notes and bills	—		—			5,929		(71		)	5,929		(71		)
Commercial paper	2,390		(2		)	—		—			2,390		(2		)
Total	$	33,201	$	(191	)	$	20,691	$	(112	)	$	53,892	$	(303	)

December 31, 2016	Less Than 12 Months					12 Months or More					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate bonds and notes	$	14,678	$	(44	)	$	13,230	$	(51	)	$	27,908	$	(95	)
Treasury and agency notes and bills	5,972		(57		)	—		—			5,972		(57		)
Commercial paper	5,216		(4		)	—		—			5,216		(4		)
Total	$	25,866	$	(105	)	$	13,230	$	(51	)	$	39,096	$	(156	)

The estimated fair value of marketable securities by contractual maturity at December 31, 2017 is shown below (in thousands). Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations without call or prepayment penalties. 

	Estimated Fair Value
Due in one year or less	$	73,889
Due in one to two years	19,180
Due in two to three years	9,776
Total	$	102,845