GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Y	Sep. 30, 2011	Dec. 31, 2011 Y
Finite-lived intangible assets
Cost	$ 237,287,000		$ 237,287,000		$ 212,188,000
Accumulated Amortization	85,477,000		85,477,000		72,544,000
Net	151,810,000		151,810,000		139,644,000
Weighted Average Amortization Period (in years)			8.9		10.0
Aggregate amortization expense	4,400,000	3,200,000	11,800,000	8,700,000
Permits
Finite-lived intangible assets
Cost	114,910,000		114,910,000		106,939,000
Accumulated Amortization	48,907,000		48,907,000		45,629,000
Net	66,003,000		66,003,000		61,310,000
Weighted Average Amortization Period (in years)			17.8		17.9
Customer relationships
Finite-lived intangible assets
Cost	98,613,000		98,613,000		83,721,000
Accumulated Amortization	25,113,000		25,113,000		17,650,000
Net	73,500,000		73,500,000		66,071,000
Weighted Average Amortization Period (in years)			7.0		7.9
Other intangible assets
Finite-lived intangible assets
Cost	23,764,000		23,764,000		21,528,000
Accumulated Amortization	11,457,000		11,457,000		9,265,000
Net	12,307,000		12,307,000		12,263,000
Weighted Average Amortization Period (in years)			3.5		5.3
Acquisition [Member] | Customer relationships
Finite-lived intangible assets
Net	12,800,000		12,800,000
Weighted Average Amortization Period (in years)			7.6
Acquisition [Member] | Other intangible assets
Finite-lived intangible assets
Net					$ 600,000
Weighted Average Amortization Period (in years)			2.8