SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Capitalized Costs Related to Natural Gas and Crude Oil Producing Activities (Unaudited) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Capitalized Costs Relating to Oil and Gas Producing Activities, by Geographic Area [Line Items]
Proved natural gas and crude oil properties	$ 3,499,718	$ 2,881,189
Unproved natural gas and crude oil properties	1,874,671	60,498
Uncompleted Wells, Equipment and Facilities	150,424	109,385
Capitalized Costs	5,524,813	3,051,072
Less accumulated DD&A	(1,534,678)	(1,131,705)
Capitalized Costs, Net	$ 3,990,135	$ 1,919,367