Oil and Gas Reserves (Unaudited) Standard Measure of Discounted Future Net Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Future Cash Inflows, Standardized Measure of Discounted Future Net Cash Flows	$ 602,501	$ 502,769	$ 931,637
Future Production Costs, Standardized Measure of Discounted Future Net Cash Flows	(213,578)	(186,695)	(280,910)
Future Development Costs, Standardized Measure of Discounted Future Net Cash Flows	(40,557)	(8,462)	(92,233)
Future Income Tax Expense, Standardized Measure of Discounted Future Net Cash Flows	(81,566)	(69,877)	(157,922)
Future Net Cash Flows, Standardized Measure of Discounted Future Net Cash Flows	266,800	237,735	400,572
10 Percent Annual Discount for Estimated Timing of Cash Flows, Standardized Measure of Discounted Future Net Cash Flows	(107,375)	(101,632)	(197,215)
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Standardized Measure	$ 159,425	$ 136,103	$ 203,357