Segment Information (Schedule of Revenues from External Customers and Long-Lived Assets) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	$ 1,171,589				$ 1,229,623				$ 1,171,589	$ 1,229,623	$ 1,339,776
Revenues	283,110	273,267	259,812	239,034	238,183	243,979	248,354	229,670	1,055,223	960,186	919,443
Drilling Services Segment [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	712,604				791,820				712,604	791,820	867,526
Drilling Services Segment [Member] | Colombia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	142,321				150,719				142,321	150,719	148,567
Revenues									$ 104,520	$ 115,631	$ 95,338
Drilling Services Segment [Member] | Colombia [Member] | Drilling Rigs [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Drilling Rigs	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	3								3		3