PROPERTY AND EQUIPMENT (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended										1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended	18 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended		18 Months Ended	6 Months Ended		18 Months Ended		12 Months Ended		3 Months Ended
	Apr. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 7 1/4% Senior Notes due 2019	Dec. 31, 2013 7 1/4% Senior Notes due 2019	Nov. 30, 2013 7 1/4% Senior Notes due 2019	Jun. 30, 2014 7 1/2% Senior Notes due 2020	Dec. 31, 2013 7 1/2% Senior Notes due 2020	Nov. 30, 2013 7 1/2% Senior Notes due 2020	Nov. 30, 2013 7 1/4% Senior Notes Due 2019 and 7 1/2% Senior Notes due 2020	Mar. 31, 2013 8 1/2% Senior Notes due 2014	May 31, 2014 Texas Panhandle	Jun. 30, 2014 Texas Panhandle	Jun. 30, 2014 Texas Panhandle		Dec. 31, 2013 Texas Panhandle	Jun. 30, 2014 Texas Panhandle	Oct. 31, 2013 Texas Panhandle	Dec. 31, 2013 Texas Panhandle Oil and Gas Properties	Jun. 30, 2014 Texas Panhandle General and Administrative Expense	Mar. 31, 2014 Texas Panhandle General and Administrative Expense	Jun. 30, 2014 Texas Panhandle General and Administrative Expense	Dec. 31, 2013 Texas Panhandle General and Administrative Expense	Jun. 30, 2014 Texas Panhandle Other, net	Dec. 31, 2013 Texas Panhandle Other, net	Jun. 30, 2014 Texas Panhandle One-time Employee Termination Benefits		Jun. 30, 2014 Texas Panhandle One-time Employee Termination Benefits	Jun. 30, 2014 Texas Panhandle Other Associated Costs		Jun. 30, 2014 Texas Panhandle Other Associated Costs		Dec. 31, 2013 South Texas	Jan. 31, 2013 South Texas	Jun. 30, 2013 South Texas One-time Employee Termination Benefits	Jun. 30, 2014 South Africa
Property, Plant and Equipment [Line Items]
General and administrative costs (including stock-based compensation) capitalized to oil and gas properties		$ 4,900,000	$ 8,100,000	$ 9,400,000	$ 20,400,000
Interest costs capitalized to unproved oil and gas properties		0	900,000	0	1,100,000
Discount factor used in full cost ceiling test (as a percent)				10.00%
Ceiling test write-down of oil and natural gas properties		77,176,000	0	77,176,000	0
Threshold for the amount of reserve quanties of a cost center for a sale that would not cause a signficant alteration between capitalized costs and estimated reserves attributable to a cost center (as a percent)				25.00%
Divestitures
Sales price of oil and natural gas properties																				1,000,000,000																325,000,000
Proceeds from sale of oil and natural gas properties														20,200,000					985,300,000																320,900,000			1,000,000
Redeemed Principal Amount of Senior Notes												700,000,000	300,000,000
Interest rate (as a percent)						7.25%	7.25%	7.25%	7.50%	7.50%	7.50%		8.50%
Gain (loss) on disposition, net		22,185,000	0	21,391,000	0										19,000,000	18,200,000		193,000,000																				3,200,000
Costs incurred, net																																					5,700,000
Exit costs reconciliation
Liability balance at beginning of period																6,935,000												1,095,000			5,840,000	[1]
Costs incurred																803,000	[2]	12,000,000			1,100,000	100,000	500,000	700,000	5,000,000	100,000	5,800,000	687,000	[2]	4,700,000	116,000	[1],[2]	8,100,000	[1]			7,500,000
Costs paid																(7,622,000)												(1,782,000)			(5,840,000)	[1]
Liability balance at end of period															116,000	116,000		6,935,000	116,000									0		0	116,000	[1]	116,000	[1]
Acquisition and development agreement [Abstract]
Drilling carry to paid by third-party per the Acquisition and Development Agreement	90,000,000
Working interest of third party	50.00%
Participation basis in future drilling for Company	50.00%
Participation basis in future drilling by Joint Venture Partner	50.00%
Realization of drilling carry				$ 70,400,000

[1] Other associated costs consist of financial advisor fees and retention bonuses paid to certain employees.

[2] Of the $.8 million costs incurred during the six months ended June 30, 2014, (i) $.7 million was recognized as an expense in “General and administrative” expense, $.5 million during the quarter ended March 31, 2014 and $.1 million during the quarter ended June 30, 2014, and (ii) $.1 million was recognized as an expense in “Other, net” during the quarter ended June 30, 2014. During the year ended December 31, 2013, $12.0 million of costs were incurred, with (i) $5.0 million recognized as an expense in “General and administrative” expense, (ii) $5.8 million recognized as an expense in “Other, net”, and (iii) $1.1 million capitalized in “Oil and natural gas properties” pursuant to the full cost method of accounting.(3)The June 30, 2014 estimated liability balance is included in “Accounts payable and accrued liabilities” in the Condensed Consolidated Balance Sheet, and Forest expects it will be paid in the third quarter of 2014.