Statements of Condensed Consolidated Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income	Noncontrolling Interests in Consolidated Subsidiaries
Balance at Dec. 31, 2011	$ 3,593,830	$ 1,261,779	$ 2,143,910	$ 188,141
Balance (in shares) at Dec. 31, 2011		149,477
Increase (Decrease) in Stockholders' Equity
Net income	140,185		135,354		4,831
Other comprehensive loss	(105,405)			(105,405)
Dividends on common stock ($0.09 and $0.66 per share for periods ending September 30, 2013 and 2012, respectively)	(98,840)		(98,840)
Stock-based compensation plans, net	35,850	35,688			162
Stock-based compensation plans, net (in shares)		136
Issuance of common units of EQT Midstream Partners, LP	276,780				276,780
Deferred taxes related to public offering of EQT Midstream Partners, LP	5,371	5,371
Balance at Sep. 30, 2012	3,847,771	1,302,838	2,180,424	82,736	281,773
Balance (in shares) at Sep. 30, 2012		149,613
Balance at Dec. 31, 2012	3,888,802	1,308,771	2,195,502	99,547	284,982
Balance (in shares) at Dec. 31, 2012		150,109
Increase (Decrease) in Stockholders' Equity
Net income	306,009		275,367		30,642
Other comprehensive loss	(22,372)			(22,372)
Dividends on common stock ($0.09 and $0.66 per share for periods ending September 30, 2013 and 2012, respectively)	(13,565)		(13,565)
Stock-based compensation plans, net	69,808	69,497			311
Stock-based compensation plans, net (in shares)		607
Distributions to noncontrolling interests ($1.12 per common unit)	(21,160)				(21,160)
Issuance of common units of EQT Midstream Partners, LP	529,442				529,442
Deferred taxes related to public offering of EQT Midstream Partners, LP	(1,641)	(1,641)
Balance at Sep. 30, 2013	$ 4,735,323	$ 1,376,627	$ 2,457,304	$ 77,175	$ 824,217
Balance (in shares) at Sep. 30, 2013		150,716