Financial Instruments and Concentration of Risk (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 Interest Rate Swaps [Member]	Sep. 30, 2012 Southern Yellow Pine [Member] Commodity Swap Contract [Member] mbf	Feb. 29, 2012 Southern Yellow Pine [Member] Commodity Swap Contract [Member] mbf	Oct. 18, 2010 Southern Yellow Pine [Member] Commodity Swap Contract [Member] mbf
Derivatives, Fair Value [Line Items]
Number of interest rate swap agreements	6
Notional amounts	$ 46.75
Debentures	22.5
Medium-term notes	$ 24.25
Swaps fixed interest rate, minimum	6.95%
Swaps fixed interest rate, maximum	8.89%
LIBOR variable interest rate, minimum	4.738%
LIBOR variable interest rate, maximum	6.518%
Derivative liability		31,200	22,500	14,300