Divestitures (Narrative) (Details)	3 Months Ended					9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) rig	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($) rig	Sep. 30, 2014 USD ($)	Mar. 31, 2014 USD ($) rig	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) rig
Property, Plant and Equipment [Line Items]
Impairment of contract drilling equipment	$ 0	$ 8,314,000		$ 0		$ 8,314,000	$ 0	$ 74,300,000
Assets held for sale	$ 5,321,000					5,321,000		$ 0
Oil and Natural Gas [Member]
Property, Plant and Equipment [Line Items]
Proceeds from non-core oil and natural gas asset sales, net of related expenses						$ 200,000	$ 18,500,000
Drilling Equipment [Member]
Property, Plant and Equipment [Line Items]
Number of drilling rigs removed from service | rig								31
Number of rigs sold | rig	30		1		4
Net book value of drilling rigs sold	$ 11,000,000		$ 300,000		$ 16,300,000
Gain (loss) on sale of drilling rigs	$ (7,300,000)		$ 7,900		$ 9,600,000