Quarterly Results (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Operating Revenues	$ 772,998	$ 685,848	$ 599,728	$ 656,469	$ 744,150	$ 767,255	$ 765,166	$ 676,335	$ 2,715,043		$ 2,952,906	$ 2,610,663
Operating income (loss)	(577,304)	(71,838)	(652,394)	185,960	263,890	295,718	282,542	232,651	(1,115,576)	[1]	1,074,801	1,021,228
Net income (loss)	(355,583)	(54,053)	(405,132)	107,704	158,533	175,173	167,454	136,609	(707,064)		637,769	603,833
Net Income (Loss) Attributable to Southwestern Energy									(707,064)		637,769	604,118
Earnings per share attributable to Southwestern Energy stockholders - Basic	$ (1.02)	$ (0.16)	$ (1.16)	$ 0.31	$ 0.47	$ 0.50	$ 0.48	$ 0.39	$ (2.03)		$ 1.84	$ 1.75
Earnings per share attributable to Southwestern Energy stockholders - Diluted	$ (1.02)	$ (0.16)	$ (1.16)	$ 0.31	$ 0.45	$ 0.50	$ 0.48	$ 0.39	$ (2.03)		$ 1.82	$ 1.73
Parent [Member]
Net income (loss)									(707,064)		637,769	604,118
Net Income (Loss) Attributable to Southwestern Energy												$ 604,118

[1] The operating loss for the E&P segment for the twelve months ended December 31, 2012 includes a $1,939.7 million non-cash ceiling test impairment of our natural gas and oil properties.