Condensed Consolidating Financial Information (Condensed Consolidating Statement of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Operating Revenues	$ 656,469		$ 676,335
Gas purchases - Midstream Services	146,676		170,230
Operating expenses	60,958		56,798
General and administrative expenses	48,826		37,117
Depreciation, depletion and amortization	193,627		163,447
Taxes, other than income taxes	20,422		16,092
Total operating costs and expenses	470,509		443,684
Operating Income	185,960		232,651
Other Income (Loss), Net	(200)	[1]	374	[1]
Equity in earnings of subsidiaries	0		0
Interest expense	7,338	[1]	7,436	[1]
Income before income taxes	178,422		225,589
Provision for income taxes	70,718	[1]	88,980	[1]
Net income attributable to Southwestern Energy	107,704		136,609
Other comprehensive income	66,570		(24,533)
Comprehensive income (loss)	174,274		112,076
Parent [Member]
Operating Revenues	0		0
Gas purchases - Midstream Services	0		0
Operating expenses	0		0
General and administrative expenses	0		0
Depreciation, depletion and amortization	0		0
Taxes, other than income taxes	0		0
Total operating costs and expenses	0		0
Operating Income	0		0
Other Income (Loss), Net	0		0
Equity in earnings of subsidiaries	107,704		136,609
Interest expense	0		0
Income before income taxes	107,704		136,609
Provision for income taxes	0		0
Net income attributable to Southwestern Energy	107,704		136,609
Other comprehensive income	254		197
Comprehensive income (loss)	107,958		136,806
Guarantors [Member]
Operating Revenues	614,445		641,843
Gas purchases - Midstream Services	146,903		170,582
Operating expenses	103,056		86,852
General and administrative expenses	41,708		32,044
Depreciation, depletion and amortization	182,837		154,401
Taxes, other than income taxes	16,998		13,907
Total operating costs and expenses	491,502		457,786
Operating Income	122,943		184,057
Other Income (Loss), Net	(174)		345
Equity in earnings of subsidiaries	0		0
Interest expense	3,755		3,645
Income before income taxes	119,014		180,757
Provision for income taxes	46,892		71,362
Net income attributable to Southwestern Energy	72,122		109,395
Other comprehensive income	65,835		(24,992)
Comprehensive income (loss)	137,957		84,403
Non-Guarantors [Member]
Operating Revenues	113,125		93,658
Gas purchases - Midstream Services	0		0
Operating expenses	27,981		27,984
General and administrative expenses	7,913		5,849
Depreciation, depletion and amortization	10,790		9,046
Taxes, other than income taxes	3,424		2,185
Total operating costs and expenses	50,108		45,064
Operating Income	63,017		48,594
Other Income (Loss), Net	(26)		29
Equity in earnings of subsidiaries	0		0
Interest expense	3,583		3,791
Income before income taxes	59,408		44,832
Provision for income taxes	23,826		17,618
Net income attributable to Southwestern Energy	35,582		27,214
Other comprehensive income	481		262
Comprehensive income (loss)	36,063		27,476
Eliminations [Member]
Operating Revenues	(71,101)		(59,166)
Gas purchases - Midstream Services	(227)		(352)
Operating expenses	(70,079)		(58,038)
General and administrative expenses	(795)		(776)
Depreciation, depletion and amortization	0		0
Taxes, other than income taxes	0		0
Total operating costs and expenses	(71,101)		(59,166)
Operating Income	0		0
Other Income (Loss), Net	0		0
Equity in earnings of subsidiaries	(107,704)		(136,609)
Interest expense	0		0
Income before income taxes	(107,704)		(136,609)
Provision for income taxes	0		0
Net income attributable to Southwestern Energy	(107,704)		(136,609)
Other comprehensive income	0		0
Comprehensive income (loss)	$ (107,704)		$ (136,609)

[1] (1) Interest income, interest expense and the provision for income taxes by segment are allocated as they are incurred at the corporate level.