DERIVATIVE INSTRUMENTS (Details) (USD $) In Thousands, unless otherwise specified																				9 Months Ended
	Oct. 01, 2011 NYMEX HH Price 3.57 Or Below [Member] Swaps Natural Gas (NYMEX HH) Calendar 2012	Oct. 01, 2011 NYMEX HH Price Range Between 4.00 and 4.50 [Member] Swaps Natural Gas (NYMEX HH) Calendar 2012	Oct. 01, 2011 NYMEX HH Price 4.50 or Above [Member] Swaps Natural Gas (NYMEX HH) Calendar 2012	Oct. 01, 2011 Minimum [Member] Swaps Natural Gas (NYMEX HH) Calendar 2012	Oct. 01, 2011 Maximum [Member] Swaps Natural Gas (NYMEX HH) Calendar 2012	Sep. 30, 2011 Swaps Natural Gas (NYMEX HH) Remaining term October 2011 to December 2011	Oct. 01, 2011 Swaps Natural Gas (NYMEX HH) Calendar 2012	Sep. 30, 2011 Swaps Natural Gas (NYMEX HH) Calendar 2012		Sep. 30, 2011 Swaps Oil (NYMEX WTI) Remaining term October 2011 to December 2011	Sep. 30, 2011 Swaps NGLs (OPIS Refined Products) Remaining term October 2011 to December 2011	Sep. 30, 2011 Swaps NGLs (OPIS Refined Products) Calendar 2012		Sep. 30, 2011 Costless Collars Oil (NYMEX WTI) Remaining term October 2011 to December 2011		Sep. 30, 2011 Swaptions Natural Gas (NYMEX HH) Term of Calendar 2012 Expires December 2011	Sep. 30, 2011 Swaptions Oil (NYMEX WTI) Term of Calendar 2012 Expires December 2011	Sep. 30, 2011 Swaptions Oil (NYMEX WTI) Term of Calendar 2013 Expires December 2012	Sep. 30, 2011 Call Options Oil (NYMEX WTI) Term of Monthly 2011 Expires Monthly in 2011	Sep. 30, 2011 Interest Rate Swaps Remaining term October 2011 to February 2014
Commodity Derivatives
Notional amount (Bbtu/Barrels per day)						150	30	105	[1]	1,000	5,000	2,000	[1]	3,000		50	3,000	2,000	1,000
Weighted Average Hedged Price per MMBtu		5.30	5.80			5.48	5.30	5.30	[1]							5.28
Weighted average ceiling price														90.20	[2]
Weighted average floor price														75.00	[2]
Weighted Average Hedged Price per Bbl										85.00	38.15	45.22	[1]				90.00	120.00	90.00
Derivative Price Per Unit Spread	1.73
Interest Rate Derivatives
Notional Amount																				$ 500,000
Reference rate for Interest Rate Swaps Weighted Average Floating Rate																				1 month LIBOR
Weighted Average Floating Rate added to reference rate (as a percent)																				5.89%
Weighted Average Fixed Rate (as a percent)																				8.50%
Derivative Price Risk Put Option Strike Price							3.57
Derivative, Price Risk Call Option Strike Price				4.00	4.50

[1] Subsequent to September 30, 2011, Forest entered into derivative agreements for the period April 2012 - December 2012 subjecting 30 Bbtu per day of the 2012 gas swaps to a written put of $3.57 and a $4.00 to $4.50 call spread whereby Forest receives $5.30 except as follows: Forest receives (i) NYMEX HH plus $1.73 when NYMEX HH is $3.57 or below; (ii) $5.30 plus the value of the call spread when NYMEX HH is between $4.00 and $4.50; and (iii) $5.80 when NYMEX HH is $4.50 or above.

[2] Represents the weighted average hedged floor and ceiling price per Bbl.