SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) In Millions, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Amount of Transitional Energy Facility Assessment and Public Utilities Assessment included in revenues and cost of sales	$ 1.2	$ 1.1	$ 5.0	$ 4.8
Amount of costs related to interests in proved and unproved properties in Pennsylvania, net of amortization	$ 3.2		$ 3.2		$ 3.3
Shares of treasury stock held (in shares)	146,406		146,406		143,546