Financial Instruments and Fair Value Measurements - Additional information (Detail) (USD $)	3 Months Ended	12 Months Ended					3 Months Ended
	Mar. 31, 2013	Dec. 31, 2008 acre	Dec. 31, 2012	Mar. 31, 2013 Defeased Debt	Dec. 31, 2012 Defeased Debt	Dec. 31, 2007 Defeased Debt	Mar. 31, 2013 Minimum	Mar. 31, 2013 Maximum
Financial Instruments And Fair Value Measurements [Line Items]
Long term debt	$ 35,752,000		$ 36,062,000	$ 26,676,000	$ 26,818,000	$ 29,300,000
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
Note maturity year							2022	2024
Retained interest	$ 9,500,000		$ 9,500,000
Retained interest, effective interest rate							3.70%	11.90%