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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair value Instruments (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Fair value measurements |  |  |  |  |
Loss on equity securities |  |  | $ 4,724 |  | $ 2,033
Acquired additional securities |  |  | 25,362 | $ 3,000 | $ 18,107
Other Assets |  |  |  |  |
Fair value measurements |  |  |  |  |
Loss on equity securities |  |  | 4,700 |  |
Acquired additional securities |  |  | 1,200 |  |
Carrying Value |  |  |  |  |
Fair value measurements |  |  |  |  |
Long-term debt | $ 86,400 |  | 86,400 | 91,000 |
Carrying Value | Other Assets |  |  |  |  |
Fair value measurements |  |  |  |  |
Strategic investments | 19,600 |  | 19,600 | 23,100 |
Short Term Investments |  |  |  |  |
Fair value measurements |  |  |  |  |
Equity investments | 200 |  | 200 | 300 |
Loss on equity securities |  |  | 100 | 300 |
Other investments |  |  |  |  |
Fair value measurements |  |  |  |  |
Equity investments | 10,200 |  | 10,200 |  |
Purchase of other investments |  |  | 10,000 |  |
Unrealized (loss) gain |  |  | 200 |  |
Other investments | Renewable energy partnership |  |  |  |  |
Fair value measurements |  |  |  |  |
Equity investments | 2,500 |  | 2,500 |  |
Equity in earnings of an unconsolidated affiliate | 100 |  |  |  |
Investment cost |  | $ 14,400 |  |  |
Investment Tax Credit |  | $ 12,000 |  |  |
Level 2 | Estimated Fair Value |  |  |  |  |
Fair value measurements |  |  |  |  |
Long-term debt | 86,900 |  | 86,900 | 91,600 |
Level 2 | Interest rate swap |  |  |  |  |
Fair value measurements |  |  |  |  |
Unrealized (loss) gain |  |  | (200) |  |
Recurring basis |  |  |  |  |
Fair value measurements |  |  |  |  |
Total assets and liabilities measured at fair value | 15,769 |  | 15,769 | 17,151 |
Recurring basis | Certificate of deposit |  |  |  |  |
Fair value measurements |  |  |  |  |
Cash and cash equivalents | 380 |  | 380 | 380 |
Recurring basis | Money market funds |  |  |  |  |
Fair value measurements |  |  |  |  |
Cash and cash equivalents | 2,329 |  | 2,329 | 2,266 |
Recurring basis | Short Term Investments |  |  |  |  |
Fair value measurements |  |  |  |  |
Investments | 416 |  | 416 | 393 |
Recurring basis | Other investments |  |  |  |  |
Fair value measurements |  |  |  |  |
Investments | 12,700 |  | 12,700 |  |
Recurring basis | Commercial paper |  |  |  |  |
Fair value measurements |  |  |  |  |
Cash and cash equivalents |  |  |  | 13,972 |
Recurring basis | Interest rate swap |  |  |  |  |
Fair value measurements |  |  |  |  |
Derivative assets |  |  |  | 140 |
Derivative liabilities | (56) |  | (56) |  |
Recurring basis | Level 1 |  |  |  |  |
Fair value measurements |  |  |  |  |
Total assets and liabilities measured at fair value | 2,745 |  | 2,745 | 2,659 |
Recurring basis | Level 1 | Money market funds |  |  |  |  |
Fair value measurements |  |  |  |  |
Cash and cash equivalents | 2,329 |  | 2,329 | 2,266 |
Recurring basis | Level 1 | Short Term Investments |  |  |  |  |
Fair value measurements |  |  |  |  |
Investments | 416 |  | 416 | 393 |
Recurring basis | Level 2 |  |  |  |  |
Fair value measurements |  |  |  |  |
Total assets and liabilities measured at fair value | 324 |  | 324 | 14,492 |
Recurring basis | Level 2 | Certificate of deposit |  |  |  |  |
Fair value measurements |  |  |  |  |
Cash and cash equivalents | 380 |  | 380 | 380 |
Recurring basis | Level 2 | Commercial paper |  |  |  |  |
Fair value measurements |  |  |  |  |
Cash and cash equivalents |  |  |  | 13,972 |
Recurring basis | Level 2 | Interest rate swap |  |  |  |  |
Fair value measurements |  |  |  |  |
Derivative assets |  |  |  | $ 140 |
Derivative liabilities | (56) |  | (56) |  |
Recurring basis | Level 3 |  |  |  |  |
Fair value measurements |  |  |  |  |
Total assets and liabilities measured at fair value | 12,700 |  | 12,700 |  |
Recurring basis | Level 3 | Other investments |  |  |  |  |
Fair value measurements |  |  |  |  |
Investments | $ 12,700 |  | $ 12,700 |  |

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes 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. + References No definition available. + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + Details
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- Definition This element represents the aggregate cost of investments accounted for under the equity method of accounting. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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 + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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- Definition Amount of realized loss from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714 + Details
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- Definition Amount of investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117539-209714 + Details
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- Definition 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. + References No definition available. + Details
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- Definition The amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; includes deferred investment tax credits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 + Details
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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
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- Definition Amount of cash outflow for purchase of marketable security. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26853-111562 + Details
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