Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment	$ 757,605	$ 603,714
Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	716,922	564,755
Equipment and Other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	18,608	17,237
Equipment and Other [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Equipment and Other [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	39 years
Drilling Rig [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	15 years
Property and equipment	$ 22,075	$ 21,722