Financial Instruments and Fair Value Measurements - Additional information (Details) (USD $)	9 Months Ended	12 Months Ended	24 Months Ended					9 Months Ended
	Sep. 30, 2013	Dec. 31, 2008 acre	Dec. 31, 2008	Dec. 31, 2012	Sep. 30, 2013 Defeased Debt	Dec. 31, 2012 Defeased Debt	Dec. 31, 2007 Defeased Debt	Sep. 30, 2013 Minimum	Sep. 30, 2013 Maximum
Financial Instruments And Fair Value Measurements [Line Items]
Long term debt	$ 37,832,000			$ 36,062,000	$ 26,404,000	$ 26,818,000	$ 29,300,000
Area of timber land sold		132,055
Maturity of notes receivables		15 years
Aggregate amount of notes receivables		183,300,000	183,300,000
Monetized notes receivables		183,300,000	183,300,000
Monetized note receivable, percentage		90.00%	90.00%
Proceeds from monetized note			163,000,000
Notes, maturity period	15 years
Note maturity year								2022	2024
Retained interest	$ 9,600,000			$ 9,500,000
Retained interest, effective interest rate								3.70%	12.40%