Condensed Consolidating Financial Information (Condensed Consolidating Statement of Operations) (Details) (USD $) In Thousands, 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		Dec. 31, 2012 Parent [Member]	Dec. 31, 2011 Parent [Member]	Dec. 31, 2010 Parent [Member]	Dec. 31, 2012 Guarantors [Member]	Dec. 31, 2011 Guarantors [Member]	Dec. 31, 2010 Guarantors [Member]	Dec. 31, 2012 Non-Guarantors [Member]	Dec. 31, 2011 Non-Guarantors [Member]	Dec. 31, 2010 Non-Guarantors [Member]	Dec. 31, 2012 Eliminations [Member]	Dec. 31, 2011 Eliminations [Member]	Dec. 31, 2010 Eliminations [Member]	Dec. 31, 2012 7.35% Senior Notes due 2017 [Member]	Dec. 31, 2012 7.125% Senior Notes due 2017 [Member]	Dec. 31, 2012 4.10% Senior Notes Due 2022 [Member]	May 31, 2012 4.10% Senior Notes Due 2022 [Member]
Debt instrument, interest rate, stated percentage																											7.35%	7.125%	4.10%	4.10%
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					$ 2,541,684	$ 2,803,385	$ 2,488,105	$ 476,997	$ 411,998	$ 318,232	$ (303,638)	$ (262,477)	$ (195,674)
Gas purchases									592,466		709,091		611,161					593,091	710,487	612,745				(625)	(1,396)	(1,584)
Operating expenses									244,735		240,944		191,771					423,147	380,154	293,713	121,953	118,713	91,164	(300,365)	(257,923)	(193,106)
General and administrative expenses									175,147		158,041		145,563					151,488	141,499	127,022	26,307	19,700	19,525	(2,648)	(3,158)	(984)
Depreciation, depletion and amortization									810,953		704,511		590,332					765,623	665,615	559,845	45,330	38,896	30,487
Impairment of natural gas and oil properties									1,939,734									1,939,734
Taxes, other than income taxes									67,584		65,518		50,608					56,262	53,950	44,200	11,321	11,568	6,408	1
Total operating costs and expenses									3,830,619		1,878,105		1,589,435					3,929,345	1,951,705	1,637,525	204,911	188,877	147,584	(303,637)	(262,477)	(195,674)
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					(1,387,661)	851,680	850,580	272,086	223,121	170,648	(1)
Other Income (Loss), Net									1,030		264		427					(1,143)	306	242	2,173	(42)	185
Equity in earnings of subsidiaries															(707,064)	637,769	604,118							707,064	(637,769)	(604,118)
Interest expense									35,657	[2]	24,075	[2]	26,163	[2]				22,312	11,277	10,777	13,345	12,798	15,386
Income (Loss) Before Income Taxes									(1,150,203)		1,050,990		995,492		(707,064)	637,769	604,118	(1,411,116)	840,709	840,045	260,914	210,281	155,447	707,063	(637,769)	(604,118)
Provision (benefit) for income taxes									(443,139)	[2]	413,221	[2]	391,659	[2]				(538,357)	332,795	330,879	95,218	80,426	60,780
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		(707,064)	637,769	604,118	(872,759)	507,914	509,166	165,696	129,855	94,667	707,063	(637,769)	(604,118)
Net Loss Attributable to Noncontrolling Interest													(285)							(285)
Net Income (Loss) Attributable to Southwestern Energy									(707,064)		637,769		604,118				604,118			509,451			94,667			(604,118)
Comprehensive income (loss)									$ (965,688)		$ 962,222		$ 603,817		$ (965,688)	$ 962,222	$ 603,817	$ (1,125,454)	$ 836,291	$ 510,626	$ 166,225	$ 129,294	$ 94,649	$ 959,229	$ (965,585)	$ (605,275)

[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.

[2] Interest income, interest expense and the provision (benefit) for income taxes by segment are an allocation of corporate amounts as cash equivalents, debt and income tax expense allocated as they are incurred at the corporate level.