Related Party Transactions (Narrative) (Details) (USD $)	1 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended			1 Months Ended		3 Months Ended	0 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended
	Oct. 31, 2012	Sep. 30, 2010	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2010 Avista Joint Venture [Member]	Sep. 30, 2010 ACP II [Member]	Jun. 30, 2011 ACP II [Member]	Jan. 15, 2013 Utica [Member] Avista Joint Venture [Member]	Oct. 31, 2012 Utica [Member] Avista Joint Venture [Member]	Dec. 31, 2012 Utica [Member] Avista Joint Venture [Member]	Oct. 31, 2012 Utica [Member] Avista Capital Partners II, L.P. [Member]	Dec. 31, 2012 Utica [Member] Avista Capital Partners II, L.P. [Member]
Related Party Transaction [Line Items]
Joint venture investment, net proceeds ownership percentage													50.00%
Joint venture investment, original ownership percentage												10.00%	10.00%
Payments to acquire interest in joint venture												$ 63,100,000	$ 24,000,000
Proceeds from sale of property	51,700,000		17,600,000	187,100,000	29,500,000	238,470,000	341,597,000	167,265,000						51,700,000		74,900,000
Joint venture, percentage of ownership increase (decrease)												40.00%
Initial ownership interest of joint interest partner															90.00%
Cost to increase ownership percentage													8.625%
Proceeds of cash distributions recognized as reductions of capitalized oil and gas property costs											78,600,000
Percentage of ownership interest sold									20.00%
Proceeds from sale of interests in joint venture										327,000,000
Percentage of interest in joint venture transferable by each party after initial cash contributions		10.00%
Due from Related Parties, Current					6,600,000	6,600,000
Advances for joint operations from affiliates					$ 2,800,000	$ 2,800,000	$ 9,800,000