Divestitures (Narrative) (Details)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) rig	Mar. 31, 2015 USD ($) rig	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($) rig	Jun. 30, 2015 USD ($) rig	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) rig
Property, Plant and Equipment [Line Items]
Proceeds from non-core oil and natural gas asset sales, net of related expenses					$ 87,000	$ 11,300,000
Number of drilling rigs removed from service | rig							31
Number of rigs sold | rig		1		4
Net book value of drilling rigs sold		$ 300,000		$ 16,300,000
Gain on sale of drilling rigs		$ 7,900		$ 9,600,000
Number of drilling rigs held for sale | rig	30				30
Impairment of contract drilling equipment	$ 8,314,000		$ 0		$ 8,314,000	0
Assets held for sale	12,649,000				12,649,000		$ 0
Gain (Loss) on Disposition of Assets	$ 415,000		$ 195,000		960,000	9,621,000
Oil and Natural Gas [Member]
Property, Plant and Equipment [Line Items]
Gain (Loss) on Disposition of Assets					$ 0	$ 0
Drilling Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairment of contract drilling equipment							$ 74,300,000