LONG-TERM DEBT AND FINANCING ARRANGEMENTS (Summary) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Long-term debt obligations
Long-term debt	$ 290,526	$ 268,919
Less current portion	54,556	61,930
Long-term debt, less current portion	235,970	206,989
Payments under long-term debt obligations
Due in one year or less	63,922
Due after one year through two years	45,366
Due after two years through three years	43,085
Due after three years through four years	149,390
Due after four years through five years	16,257
Due after five years	1,771
Total payments	319,791
Less amounts representing interest	29,265
Long-term debt	290,526	268,919
Credit Facility
Long-term debt obligations
Long-term debt	$ 70,000	70,000
Interest rate (as a percent)	3.50%
Payments under long-term debt obligations
Due in one year or less	$ 2,752
Due after one year through two years	3,041
Due after two years through three years	3,030
Due after three years through four years	72,292
Total payments	81,115
Less amounts representing interest	11,115
Long-term debt	70,000	70,000
Credit Facility | Interest rate swap agreement
Long-term debt obligations
Amount of borrowings covered by the interest rate swap	$ 50,000
Effective fixed interest rate on hedged borrowings (as a percent)	3.10%
Accounts receivable securitization borrowings
Long-term debt obligations
Long-term debt	$ 45,000	45,000
Interest rate (as a percent)	3.00%
Payments under long-term debt obligations
Due in one year or less	$ 1,609
Due after one year through two years	1,794
Due after two years through three years	1,789
Due after three years through four years	45,151
Total payments	50,343
Less amounts representing interest	5,343
Long-term debt	45,000	45,000
Notes payable
Long-term debt obligations
Long-term debt	$ 175,206	153,441
Weighted-average interest rate (as a percent)	3.30%
Payments under long-term debt obligations
Due in one year or less	$ 59,323
Due after one year through two years	40,446
Due after two years through three years	38,259
Due after three years through four years	31,944
Due after four years through five years	16,257
Due after five years	1,771
Total payments	188,000
Less amounts representing interest	12,794
Long-term debt	175,206	153,441
Capital lease obligations
Long-term debt obligations
Long-term debt	$ 320	478
Weighted-average interest rate (as a percent)	5.60%
Payments under long-term debt obligations
Due in one year or less	$ 238
Due after one year through two years	85
Due after two years through three years	7
Due after three years through four years	3
Total payments	333
Less amounts representing interest	13
Long-term debt	$ 320	$ 478