CASH EQUIVALENTS AND INVESTMENTS - Schedule of Short-Term Investments by Measurement (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	$ 1,254	$ 6,619
Marketable securities, fair value	17,224	61,836
Investments, fair value	9,031	32,371
Quoted prices in active markets (Level 1)
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	1,254	6,619
Marketable securities, fair value	0	0
Investments, fair value	0	0
Significant other observable inputs (Level 2)
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	0	0
Marketable securities, fair value	17,224	61,836
Investments, fair value	9,031	32,371
Significant unobservable inputs (Level 3)
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	0	0
Marketable securities, fair value	0	0
Investments, fair value	0	0
Municipal obligations
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value		3,261
Municipal obligations \| Quoted prices in active markets (Level 1)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value		0
Municipal obligations \| Significant other observable inputs (Level 2)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value		3,261
Municipal obligations \| Significant unobservable inputs (Level 3)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value		0
U.S. government agency notes
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	4,072	16,477
Investments, fair value	3,964	19,437
U.S. government agency notes \| Quoted prices in active markets (Level 1)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
U.S. government agency notes \| Significant other observable inputs (Level 2)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	4,072	16,477
Investments, fair value	3,964	19,437
U.S. government agency notes \| Significant unobservable inputs (Level 3)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Corporate debt securities
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	8,017	41,852
Investments, fair value	3,884	10,476
Corporate debt securities \| Quoted prices in active markets (Level 1)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Corporate debt securities \| Significant other observable inputs (Level 2)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	8,017	41,852
Investments, fair value	3,884	10,476
Corporate debt securities \| Significant unobservable inputs (Level 3)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Certificates of deposit
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	5,135	246
Investments, fair value	1,183	2,458
Certificates of deposit \| Quoted prices in active markets (Level 1)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Certificates of deposit \| Significant other observable inputs (Level 2)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	5,135	246
Investments, fair value	1,183	2,458
Certificates of deposit \| Significant unobservable inputs (Level 3)
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	$ 0	$ 0

Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26626-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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