SEGMENT AND GEOGRAPHIC DISCLOSURES - Geographic Breakdown of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Revenues from External Customers [Line Items]
Revenues	$ 269,599	$ 302,385
United States
Revenues from External Customers [Line Items]
Revenues	206,108	233,376
Canada
Revenues from External Customers [Line Items]
Revenues	19,321	27,368
Europe
Revenues from External Customers [Line Items]
Revenues	28,496	28,225
Other foreign countries
Revenues from External Customers [Line Items]
Revenues	$ 15,674	$ 13,416

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration