Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2012

Summary of property, plant and equipment

	Useful	December 31,
(Thousands of dollars)	Lives	2012			2011
Land and improvements	0-15 years	$	186,971		$	173,517
Buildings and improvements	30 years	384,535			376,659
Machinery and equipment	3-20 years	942,631			794,435
Vessels and vehicles	3-18 years	157,368			147,125
Office furniture and fixtures	5 years	29,972			28,376
Construction in progress		42,879			136,396
		1,744,356			1,656,508
Accumulated depreciation and amortization		(900,477		)	(859,686		)
Net property, plant and equipment		$	843,879		$	796,822

- Definition

Tabular disclosure of the useful life and salvage value of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

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