Property and Equipment (Schedule of estimated useful lives and costs of asset classes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,093,635	$ 1,058,261
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 47,932	45,424
Vehicles [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Vehicles [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 12,717	11,628
Office Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Office Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 24,013	23,884
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Not Yet Placed in Service [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 6,751	9,050
Not Yet Placed in Service [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	0 years
Not Yet Placed in Service [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	0 years
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,367	2,367
Land [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	0 years
Land [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	0 years
Drilling Services [Member] | Drilling Rigs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 594,743	582,477
Drilling Services [Member] | Drilling Rigs [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	25 years
Drilling Services [Member] | Drilling Rigs [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Well Servicing [Member] | Production Services [Member] | Well Service Rigs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 244,747	225,125
Well Servicing [Member] | Production Services [Member] | Well Service Rigs [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years
Well Servicing [Member] | Production Services [Member] | Well Service Rigs [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Wireline Services [Member] | Production Services [Member] | Wireline Units [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 142,224	141,959
Wireline Services [Member] | Production Services [Member] | Wireline Units [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Wireline Services [Member] | Production Services [Member] | Wireline Units [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	1 year
Coiled Tubing Services [Member] | Production Services [Member] | Coiled Tubing Units [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 18,141	$ 16,347
Coiled Tubing Services [Member] | Production Services [Member] | Coiled Tubing Units [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Coiled Tubing Services [Member] | Production Services [Member] | Coiled Tubing Units [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	1 year