Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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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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Total revenue reported by the acquired entity for its previous full fiscal year before the business acquisition.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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Amount of liabilities assumed at the acquisition date.

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The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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Represents the number of stores.

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ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	9 Months Ended		12 Months Ended
ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	Sep. 30, 2016 USD ($) branches	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) branches
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 78,564	$ 89,786
Payments to Acquire Businesses, Gross	50,745	68,502
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	26,764	21,284
Payments to Acquire Businesses, Gross	$ 51,800	68,502
Number of Stores \| branches	500
Cash Acquired from Acquisition	$ (1,055)	$ 0
Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 14, 2016
Business Acquisition, Name of Acquired Entity	Atlanta Electrical Distributors, LLC
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 85,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	21,800
Goodwill, Acquired During Period	$ 31,600
Number of Stores	5
Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			May 01, 2015
Business Acquisition, Name of Acquired Entity			Hill Country Electric Supply, LP
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 140,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			21,100
Goodwill, Acquired During Period			$ 16,200
Number of Stores \| branches			9
Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Oct. 30, 2015
Business Acquisition, Name of Acquired Entity			Needham Electric Supply Corporation
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 115,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			31,000
Goodwill, Acquired During Period			$ 35,700
Number of Stores \| branches			24
Customer Relationships [Member] \| Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 15,800
Customer Relationships [Member] \| Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 13,100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			11 years
Customer Relationships [Member] \| Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 24,500
Noncompete Agreements [Member] \| Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years
Noncompete Agreements [Member] \| Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 200
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			5 years
Trademarks [Member] \| Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 6,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Trademarks [Member] \| Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 7,800
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			12 years
Trademarks [Member] \| Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 6,500
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			13 years
Minimum [Member] \| Customer Relationships [Member] \| Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Minimum [Member] \| Customer Relationships [Member] \| Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			12 years
Maximum [Member] \| Customer Relationships [Member] \| Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	14 years
Maximum [Member] \| Customer Relationships [Member] \| Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			14 years