Fair Value Measurements (Details 1) (Fair value on a non-recurring basis [Member], USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Assets (Liabilities)
Total	$ (2,497)	$ (1,470)
Asset retirement obligations [Member]
Assets (Liabilities)
Asset retirement obligations	(2,497)	(1,470)
Level 1 [Member]
Assets (Liabilities)
Total
Level 1 [Member] | Asset retirement obligations [Member]
Assets (Liabilities)
Asset retirement obligations	0	0
Level 2 [Member]
Assets (Liabilities)
Total
Level 2 [Member] | Asset retirement obligations [Member]
Assets (Liabilities)
Asset retirement obligations	0	0
Level 3 [Member]
Assets (Liabilities)
Total	(2,497)	(1,470)
Level 3 [Member] | Asset retirement obligations [Member]
Assets (Liabilities)
Asset retirement obligations		(1,470)
Asset Retirement Obligation, Period Increase (Decrease)	$ (2,497)