SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Capitalized Costs Related to Natural Gas and Crude Oil Producing Activities (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Capitalized Costs Relating to Oil and Gas Producing Activities, by Geographic Area [Line Items]
Proved natural gas and crude oil properties	$ 2,075,924	$ 1,694,847
Unproved natural gas and crude oil properties	319,327	102,466
Capitalized Costs, Oil and Gas Producing Activities, Gross	2,395,251	1,797,313
Less accumulated DD&A	(905,458)	(621,074)
Capitalized Costs, Oil and Gas Producing Activities, Net	$ 1,489,793	$ 1,176,239

SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Capitalized Costs Related to Natural Gas and Crude Oil Producing Activities (Unaudited) (Details) (USD $)
In Thousands, unless otherwise specified

Dec. 31, 2012

Dec. 31, 2011

Capitalized Costs Relating to Oil and Gas Producing Activities, by Geographic Area [Line Items]

Proved natural gas and crude oil properties

$ 2,075,924

$ 1,694,847

Unproved natural gas and crude oil properties

319,327

102,466

Capitalized Costs, Oil and Gas Producing Activities, Gross

2,395,251

1,797,313

Less accumulated DD&A

(905,458)

(621,074)

Capitalized Costs, Oil and Gas Producing Activities, Net

$ 1,489,793

$ 1,176,239

- Definition

Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table.

+ References+ Details

- Definition

Capitalized costs of unproved properties incurred for any combination mineral interests acquisitions and other costs not previously disclosed within this table.

+ References+ Details