Segment Information (Schedule of Revenues from External Customers and Long-Lived Assets) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) drilling_rigs	Jun. 30, 2014 USD ($) drilling_rigs	Jun. 30, 2015 USD ($) drilling_rigs	Jun. 30, 2014 USD ($) drilling_rigs	Dec. 31, 2014 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	$ 1,004,897	$ 1,251,431	$ 1,004,897	$ 1,251,431	$ 1,171,589
Revenues	135,011	259,812	328,825	498,846
Drilling Services Segment [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	$ 574,050	778,148	$ 574,050	778,148
Drilling Rigs | drilling_rigs	35		35
Drilling Services Segment [Member] | Colombia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	$ 65,902	157,025	$ 65,902	157,025
Revenues	$ 14,078	$ 25,527	$ 34,039	$ 47,691
Drilling Rigs | drilling_rigs	8		8
Drilling Services Segment [Member] | Colombia [Member] | Drilling Rigs [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling Rigs | drilling_rigs	5	5	5	5
Drilling Services Segment [Member] | Colombia [Member] | Assets Leased From Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling Rigs | drilling_rigs	3	3	3	3