ACQUISITIONS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business acquisition, shares issued	582,233
Share issue price per share	$ 28.19
Materials and supplies	$ 14,078	$ 12,251
Equipment and property, net	101,669	87,215
Goodwill	255,563	211,847	212,477
Customer contracts	104,657	101,457
Other intangible assets	28,815	27,112
Current liabilities	252,679	235,792
Business Acquisitions [Member]
Accounts receivable, net	2,594
Materials and supplies	481
Prepaid expenses	175
Equipment and property, net	4,516
Goodwill	48,477
Customer contracts	28,237
Other intangible assets	6,471
Current liabilities	(6,733)
Other assets and liabilities, net	(2,900)
Total consideration paid	81,318
Less: Common Stock Payment	(16,413)
Less: Contingent consideration liability	(1,570)
Total cash purchase price for the Company's acquisitions	$ 63,335