Retained Interest Investments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2008 acre	Dec. 31, 2011
Other Ownership Interests [Line Items]
Area of timber land sold		132,055
Maturity of notes receivables		Fifteen year
Aggregate amount of notes receivables		$ 183,300,000
Monetized notes receivables		183,300,000
Proceeds from monetized note		163,000,000
Notes, maturity period	15 years
Retained interest	$ 9,481,000		$ 10,707,000
Minimum
Other Ownership Interests [Line Items]
Note maturity year	2022
Retained interest, effective interest rate	3.70%
Maximum
Other Ownership Interests [Line Items]
Note maturity year	2024
Retained interest, effective interest rate	11.90%