Gains on Dispositions of Plant, Equipment and Timberlands, Net - Additional Information (Detail) $ in Thousands		3 Months Ended			9 Months Ended
	Oct. 09, 2015 USD ($) a	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Property, Plant and Equipment [Line Items]
Proceeds from sale of timberlands					$ 3,181	$ 4,051
After-tax gain on timberlands			$ 123	$ 1,590	$ 2,888	$ 3,881
Timber Properties [Member] | Scenario, Forecast [Member]
Property, Plant and Equipment [Line Items]
After-tax gain on timberlands		$ 9,100
Timber Properties [Member] | Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Acres of timberlands | a	9,803
Proceeds from sale of timberlands	$ 17,000