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Marketable Securities and Fair Value Disclosures | 12 Months Ended
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Dec. 31, 2017
Marketable Securities And Fair Value Disclosures [Abstract] |
Marketable Securities and Fair Value Disclosures | (3) Marketable Securities and Fair Value Disclosures Marketable securities consisted of the following as of December 31, 2017 and 2016 (in thousands):
| December 31, 2017 |
|  |  |  |  | Gross |  |  | Gross |  |  |  |  |
| Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
| Cost |  |  | Gains |  |  | Losses |  |  | Value |
Short-term available-for-sale securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds | $ | 3,052 |  |  | $ | — |  |  | $ | (2 | ) |  | $ | 3,050 |
Total | $ | 3,052 |  |  | $ | — |  |  | $ | (2 | ) |  | $ | 3,050 |
| December 31, 2016 |
|  |  |  |  | Gross |  |  | Gross |  |  |  |  |
| Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
| Cost |  |  | Gains |  |  | Losses |  |  | Value |
Short-term available-for-sale securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds | $ | 13,778 |  |  | $ | — |  |  | $ | (16 | ) |  | $ | 13,762 |
Total | $ | 13,778 |  |  | $ | — |  |  | $ | (16 | ) |  | $ | 13,762 |
Long-term available-for-sale securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds | $ | 2,355 |  |  | $ | 3 |  |  | $ | (6 | ) |  | $ | 2,352 |
Total | $ | 2,355 |  |  | $ | 3 |  |  | $ | (6 | ) |  | $ | 2,352 |
The investments have been in an unrealized loss position for less than twelve months. Based upon the Company’s evaluation of all relevant factors, the Company believes that the decline in fair value of securities held at December 31, 2017 below cost is temporary, and the Company intends to retain its investment in these securities for a sufficient period of time to allow for recovery of the fair value. As of December 31, 2017, the amortized cost and estimated fair value of available-for-sale securities by contractual maturity were as follows (in thousands):
| Amortized |  |  | Fair |
| Cost |  |  | Value |
Due in one year or less | $ | 3,052 |  |  | $ | 3,050 |
Total | $ | 3,052 |  |  | $ | 3,050 |
Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). Inputs used to measure fair value are classified into the following hierarchy:
| • | Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities. The Company’s Level 1 assets consist of money market investments. The Company does not have any Level 1 liabilities.
| • | Level 2—Unadjusted quoted prices in active markets for similar assets or liabilities; unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active; or inputs other than quoted prices that are observable for the asset or liability. The Company’s Level 2 assets consist of corporate bonds and commercial paper securities. The Company does not have any Level 2 liabilities.
| • | Level 3—Unobservable inputs for the asset or liability. The Company does not have any Level 3 assets or liabilities.
The following table identifies the Company’s assets that were measured at fair value on a recurring basis (in thousands):
| Balance |  |  | Level 1 |  |  | Level 2 |  |  | Level 3 |
December 31, 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market | $ | 8,189 |  |  | $ | 8,189 |  |  | $ | — |  |  | $ | — |
Corporate bonds |  | 3,725 |  |  |  | — |  |  |  | 3,725 |  |  |  | — |
Total | $ | 11,914 |  |  | $ | 8,189 |  |  | $ | 3,725 |  |  | $ | — |
December 31, 2016 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market | $ | 7,672 |  |  | $ | 7,672 |  |  | $ | — |  |  | $ | — |
Corporate bonds |  | 16,114 |  |  |  | — |  |  |  | 16,114 |  |  |  | — |
Total | $ | 23,786 |  |  | $ | 7,672 |  |  | $ | 16,114 |  |  | $ | — |
As of December 31, 2017 and 2016, the Company had $8.9 million and $7.7 million, respectively, of cash equivalents consisting of money market funds and corporate bonds with original maturities of 90 days or less. The Company has the ability to liquidate these investments without restriction. The Company determines fair value for these money market funds and equity securities with Level 1 inputs through quoted market prices. There were no transfers between any fair value hierarchy levels in 2017 or 2016. Fair Value of Other Financial Instruments The carrying amount of other financial instruments, including accounts payable, approximated fair value due to their short maturities. As of December 31, 2017 and 2016, the Company did not have any debt outstanding.

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