Derivatives Derivative (Details-Textuals) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Derivatives
Expected change in fair value of outstanding derivative due to change in underlying asset	$ 3.2
Price of Oil [Member]
Derivatives
Expected change in fair value of outstanding derivative, change in price of underlying asset, per unit (in dollars per unit)	1
Price of Gas [Member]
Derivatives
Expected change in fair value of outstanding derivative, change in price of underlying asset, per unit (in dollars per unit)	0.50