Cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land or leased assets).

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Gross amount of long-lived physical assets excluding assets held under lease agreements used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets excluding assets held under lease agreements used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Property and equipment
Property and equipment, gross	$ 756,124		$ 739,386
Less accumulated depreciation and impairment	(500,541)		(490,519)
Total property and equipment, net	255,583		248,867
Capital lease obligations	0	$ 0
Land
Property and equipment
Property and equipment, gross	8,540		8,593
Building and leasehold improvements
Property and equipment
Property and equipment, gross	83,061		83,352
Vehicles and equipment
Property and equipment
Property and equipment, gross	27,711		24,114
Machinery and equipment
Property and equipment
Property and equipment, gross	538,693		534,303
Computer equipment and software
Property and equipment
Property and equipment, gross	11,221		11,102
Office furniture and equipment
Property and equipment
Property and equipment, gross	4,277		4,275
Disposal wells
Property and equipment
Property and equipment, gross	67,566		67,566
Helicopters
Property and equipment
Property and equipment, gross	497		497
Construction in progress
Property and equipment
Property and equipment, gross	$ 14,558		$ 5,584