Condensed Consolidating Financial Information (Condensed Consolidating Statement of Operations) (Details) (USD $) In Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Revenues from external customers	$ 767,255		$ 682,172		$ 2,208,756		$ 1,940,232
Gas purchases - midstream services	175,236		158,095		545,518		457,555
Operating expenses	63,911		52,929		175,763		140,438
General and administrative expenses	35,600		35,158		112,955		104,735
Depreciation, depletion and amortization	179,113		151,284		514,180		434,307
Taxes, other than income taxes	17,677		14,570		49,429		38,654
Total operating costs and expenses	471,537		412,036		1,397,845		1,175,689
Operating Income	295,718		270,136		810,911		764,543
Other income (loss), net	(122)		326		321		265
Interest expense	5,657	[1]	6,589	[1]	19,263	[1]	19,277	[1]
Income before income taxes	289,939		263,873		791,969		745,531
Provision (benefit) for income taxes	114,766	[1]	103,235	[1]	312,733	[1]	291,116	[1]
Net income	175,173		160,638		479,236		454,415
Less: Net Loss Attributable to noncontrolling interest	0		(103)		0		(192)
Net income (loss) attributable to Southwestern Energy	175,173		160,741		479,236		454,607
Parent [Member]
Equity in earnings of subsidiaries	175,173		160,741		479,236		454,607
Income before income taxes	175,173		160,741		479,236		454,607
Net income	175,173		160,741		479,236		454,607
Net income (loss) attributable to Southwestern Energy	175,173		160,741		479,236		454,607
Guarantors [Member]
Revenues from external customers	730,826		648,605		2,101,099		1,853,194
Gas purchases - midstream services	175,729		158,503		546,731		458,788
Operating expenses	101,645		78,113		276,974		211,252
General and administrative expenses	34,030		31,041		101,372		91,270
Depreciation, depletion and amortization	169,446		143,202		485,546		412,217
Taxes, other than income taxes	13,731		13,014		41,206		34,461
Total operating costs and expenses	494,581		423,873		1,451,829		1,207,988
Operating Income	236,245		224,732		649,270		645,206
Other income (loss), net	(16)		214		345		74
Interest expense	2,376		1,716		7,769		5,526
Income before income taxes	233,853		223,230		641,846		639,754
Provision (benefit) for income taxes	92,725		87,387		253,738		249,866
Net income	141,128		135,843		388,108		389,888
Less: Net Loss Attributable to noncontrolling interest			(103)				(192)
Net income (loss) attributable to Southwestern Energy	141,128		135,946		388,108		390,080
Non-Guarantors [Member]
Revenues from external customers	105,486		85,602		299,252		227,625
Operating expenses	30,034		26,197		86,811		67,801
General and administrative expenses	2,366		4,363		13,943		14,204
Depreciation, depletion and amortization	9,667		8,082		28,634		22,090
Taxes, other than income taxes	3,946		1,556		8,223		4,193
Total operating costs and expenses	46,013		40,198		137,611		108,288
Operating Income	59,473		45,404		161,641		119,337
Other income (loss), net	(106)		112		(24)		191
Interest expense	3,281		4,873		11,494		13,751
Income before income taxes	56,086		40,643		150,123		105,777
Provision (benefit) for income taxes	22,041		15,848		58,995		41,250
Net income	34,045		24,795		91,128		64,527
Net income (loss) attributable to Southwestern Energy	34,045		24,795		91,128		64,527
Eliminations [Member]
Revenues from external customers	(69,057)		(52,035)		(191,595)		(140,587)
Gas purchases - midstream services	(493)		(408)		(1,213)		(1,233)
Operating expenses	(67,768)		(51,381)		(188,022)		(138,615)
General and administrative expenses	(796)		(246)		(2,360)		(739)
Total operating costs and expenses	(69,057)		(52,035)		(191,595)		(140,587)
Equity in earnings of subsidiaries	(175,173)		(160,741)		(479,236)		(454,607)
Income before income taxes	(175,173)		(160,741)		(479,236)		(454,607)
Net income	(175,173)		(160,741)		(479,236)		(454,607)
Net income (loss) attributable to Southwestern Energy	$ (175,173)		$ (160,741)		$ (479,236)		$ (454,607)

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