Assets (Details 3) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		$ 419,902,000	$ 445,640,000
Less: accumulated depreciation and amortization		(272,109,000)	(235,281,000)
Property and equipment, net, excluding asset under construction		147,793,000	210,359,000
Property and equipment, net		150,037,000	212,636,000
Depreciation expense		70,500,000	69,900,000	68,900,000
Interest costs capitalized		0	0	1,100,000
Net loss on equipment			200,000
Insurance proceeds	2,100,000		1,500,000
Field operating equipment
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		302,006,000	318,530,000
Field operating equipment | Minimum
Property and Equipment, Net
Estimated Useful Life		3 years
Field operating equipment | Maximum
Property and Equipment, Net
Estimated Useful Life		10 years
Vehicles
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		70,398,000	76,849,000
Vehicles | Minimum
Property and Equipment, Net
Estimated Useful Life		3 years
Vehicles | Maximum
Property and Equipment, Net
Estimated Useful Life		10 years
Buildings and improvements
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		8,266,000	10,948,000
Buildings and improvements | Minimum
Property and Equipment, Net
Estimated Useful Life		6 years
Buildings and improvements | Maximum
Property and Equipment, Net
Estimated Useful Life		39 years
Software
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		26,254,000	25,554,000
Software | Minimum
Property and Equipment, Net
Estimated Useful Life		3 years
Software | Maximum
Property and Equipment, Net
Estimated Useful Life		5 years
Data processing equipment
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		9,120,000	9,765,000
Data processing equipment | Minimum
Property and Equipment, Net
Estimated Useful Life		3 years
Data processing equipment | Maximum
Property and Equipment, Net
Estimated Useful Life		5 years
Furniture and equipment
Property and Equipment, Net
Property and equipment before accumulated depreciation and assets under construction		3,858,000	3,994,000
Furniture and equipment | Minimum
Property and Equipment, Net
Estimated Useful Life		3 years
Furniture and equipment | Maximum
Property and Equipment, Net
Estimated Useful Life		5 years
Assets under construction
Property and Equipment, Net
Property and equipment, net		2,244,000	2,277,000
Libya
Property and Equipment, Net
Property and equipment, net		$ 0