Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data	Jun. 30, 2011	Dec. 31, 2010
PLUM CREEK TIMBER CO INC [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	75.0	75.0
Preferred stock, outstanding shares	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized shares	300.6	300.6
Common stock, outstanding (net of Treasury stock)	162.0	161.6
Treasury stock, common shares	26.2	26.2
PLUM CREEK TIMBERLANDS L P [Member]
Investment in Grantor Trusts, amounts at Fair Value	$ 38	$ 35