Litigation and Environmental Contingencies - Environmental (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) a
Antioch, California
Environmental Exit Cost [Line Items]
Area of land not sold (in acres)		25
Area of land (in acres)		289
Area sold without certificate of completion under voluntary remediation program		80
Wyoming
Environmental Exit Cost [Line Items]
Environmental liability | $	$ 1,155,000
Paper Manufacturing Sites
Environmental Exit Cost [Line Items]
Insurance policy | $		$ 20,000,000
Length of insurance policy (in years)		10 years