Bistineau Storage Gas Loss (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Storage Gas Loss [Abstract]
Volumn of gas loss (in Bcf)	6.7
Value of gas loss	$ 3.7	$ 0
Carrying value of gas per MMBtu (in dollars per MMBtu)	0.53