Supplemental Gas Data Exploratary Wells (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Less than one year	$ 17,728
Greater than One Year	0
Total	17,728
Costs expensed due to determination of dry hole or abandonment of project	8,596	3,320	5,108
Costs reclassified to wells, equipment and facilities based on the determination of proved reserves	$ 12,140	$ 14,447	$ 189