Oil and Gas Properties (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Proven Properties [Abstract]
Acquisition, equipment, exploration, drilling and evnironmental costs	$ 7,817,374,000	$ 7,235,765,000
Less: Accumulated depletion, depreciation and amortization	(5,808,836,000)	(5,578,265,000)
Proved	2,008,538,000	1,657,500,000
Unproven Properties:
Unproven properties not being amortized	413,073,000	0
Net capitalized costs - oil and gas properties	$ 2,421,611,000	$ 1,657,500,000