INDEBTEDNESS (NARRATIVE) (Details) $ in Thousands				12 Months Ended
	Dec. 31, 2019 USD ($)	Feb. 14, 2019	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)
Initial Borrowing Capacity	$ 900,000			$ 900,000
Maximum borrowing capacity	1,200,000			$ 1,200,000
Line of Credit Facility, Interest Rate Description		Base rate loans bear interest at a rate equal to the greatest of (i) Wells Fargo's prime rate, (ii) one half of 1% in excess of the federal funds effective rate, and (iii) 1.25% in excess of the one month London Interbank Offered Rate ("LIBOR"); plus in each case a margin of 0% to 0.75% based on the Company's net leverage ratio. Eurodollar loans bear interest at LIBOR plus a margin of 1.0% to 1.75% based on the Company's net leverage ratio. Alternate currency loans bear interest at rates applicable to their respective currencies.
Description of line of credit agreement		On February 14, 2019, the Company entered into a Fourth Amendment to its Amended and Restated Credit Agreement and Amended and Restated Security Agreement originally dated as of June 3, 2013 (collectively the "Credit Agreement") for a senior secured revolving credit facility with a syndicate of lenders led by Wells Fargo Bank, National Association, as agent, swing line and fronting lender (the "Credit Facility"). The amended Credit Agreement provides for a secured revolving Credit Facility that matures on February 14, 2024.Other than the extension of the Credit Facility's maturity date and a few material terms outlined below, the material terms of the Credit Facility, including pricing and collateral, are substantially the same as those previously disclosed as part of the Company's Annual Report on Form 10-K for the period ended December 31, 2015 ("2016 Credit Facility").The maximum commitment under the Credit Facility is $900.0 million with an accordion feature of up to $1.2 billion in the aggregate, if certain conditions are satisfied. The Credit Facility commitment fees are payable to the lenders in an amount equal to the unused portion of the Credit Facility multiplied by a rate per annum as determined by reference to the Company's net leverage ratio. The Credit Agreement contains customary affirmative, negative, and financial covenants, which remained unchanged from the 2016 Credit Facility, except that the Company is now obligated to maintain a maximum net leverage ratio of 3.50 to 1.00, and a minimum Interest Coverage Ratio of 2.50 to 1.00. The Credit Agreement permits accounts receivable factoring up to the greater of $75 million or 25 percent of the average book value of all accounts receivable over the most recent twelve month period.
Line of Credit Facility, Collateral				Letter of credit fees are one eighth of 1% of the stated amount of the letter of credit on the date of issuance, renewal or amendment, plus an annual fee equal to the borrowing margin for Eurodollar loans.
Borrowings outstanding on credit facility	290,000		$ 282,000	$ 290,000
Average daily utilization under credit facility	331,800		$ 514,700
Remaining borrowing capacity under credit facility	$ 530,000			$ 530,000
Minimum
Ratio of Indebtedness to Net Capital	3.50			3.50
Maximum
Ratio of Indebtedness to Net Capital	1.00			1.00