Net Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2013

Net Property, Plant and Equipment

Summary of property, plant and equipment

	Useful	December 31,
(Thousands of dollars)	Lives	2013			2012
Land and improvements	0-15 years	$	194,237		$	186,971
Buildings and improvements	30 years	395,598			384,535
Machinery and equipment	3-20 years	990,553			942,631
Vessels and vehicles	3-18 years	126,502			157,368
Office furniture and fixtures	5 years	30,102			29,972
Construction in progress		40,317			42,879
		1,777,309			1,744,356
Accumulated depreciation and amortization		(913,736		)	(900,477		)
Net property, plant and equipment		$	863,573		$	843,879