Gains (Losses) on Dispositions of Plant, Equipment and Timberlands (Summary for Sale of Timberlands and Other Assets) (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($) a	Mar. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Proceeds	$ 1,695
Gain (loss)	$ 1,554	$ (32)
Timberlands [Member]
Property, Plant and Equipment [Line Items]
Acres \| a	426
Proceeds	$ 1,156
Gain (loss)	1,115
Other [Member]
Property, Plant and Equipment [Line Items]
Proceeds	539
Gain (loss)	$ 439	$ (32)

Area of land held.

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- Definition

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

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- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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