STOCKHOLDERS' EQUITY - Summary of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Foreign currency translation	$ (33,377)	$ (45,580)
Accumulated unrealized gain on government-sponsored pooled loan investments	630	802
Other	18,273	9,658
Total accumulated other comprehensive loss	$ (14,474)	$ (35,120)

Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e681-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section 45
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-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=64808268&loc=d3e32022-110900

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 830
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901

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