LONG-TERM DEBT AND FINANCING ARRANGEMENTS (Summary) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Long-term debt obligations
Long-term debt	$ 257,318	$ 243,673
Less current portion	62,588	64,143
Long-term debt, less current portion	194,730	179,530
Payments under long-term debt obligations
Due in one year or less	68,166
Due after one year through two years	45,379
Due after two years through three years	135,177
Due after three years through four years	13,459
Due after four years through five years	9,160
Due after five years	257
Total payments	271,598
Less amounts representing interest	14,280
Long-term debt	257,318	243,673
Credit Facility
Long-term debt obligations
Long-term debt	$ 70,000	70,000
Interest rate (as a percent)	2.70%
Payments under long-term debt obligations
Due in one year or less	$ 2,026
Due after one year through two years	2,251
Due after two years through three years	71,199
Total payments	75,476
Less amounts representing interest	5,476
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)	3.35%
Accounts receivable securitization program
Long-term debt obligations
Long-term debt	$ 45,000	35,000
Interest rate (as a percent)	2.00%
Payments under long-term debt obligations
Due in one year or less	$ 1,029
Due after one year through two years	1,173
Due after two years through three years	45,948
Total payments	48,150
Less amounts representing interest	3,150
Long-term debt	45,000	35,000
Notes payable
Long-term debt obligations
Long-term debt	$ 141,741	138,032
Weighted-average interest rate (as a percent)	2.40%
Payments under long-term debt obligations
Due in one year or less	$ 64,880
Due after one year through two years	41,718
Due after two years through three years	17,887
Due after three years through four years	13,452
Due after four years through five years	9,155
Due after five years	257
Total payments	147,349
Less amounts representing interest	5,608
Long-term debt	141,741	138,032
Capital lease obligations
Long-term debt obligations
Long-term debt	$ 577	641
Weighted-average interest rate (as a percent)	5.70%
Payments under long-term debt obligations
Due in one year or less	$ 231
Due after one year through two years	237
Due after two years through three years	143
Due after three years through four years	7
Due after four years through five years	5
Total payments	623
Less amounts representing interest	46
Long-term debt	$ 577	$ 641