CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating revenues:
Natural gas gathering and processing	$ 1,179,680	$ 1,008,023	$ 732,251
Natural gas distribution	666,650	698,513	692,904
Natural gas transportation and storage	803,650	769,450	749,161
Other	15,974	13,927	4,702
Total operating revenues	2,665,954	2,489,913	2,179,018
Operating expenses:
Cost of natural gas and other energy	1,362,177	1,243,749	1,060,892
Operating, maintenance and general	498,255	463,517	468,721
Depreciation and amortization	237,690	228,637	213,827
Revenue-related taxes	35,608	37,619	36,375
Taxes, other than on income and revenues	54,366	55,776	53,114
Total operating expenses	2,188,096	2,029,298	1,832,929
Operating income	477,858	460,615	346,089
Other income (expenses):
Interest expense	(219,232)	(216,665)	(196,800)
Earnings from unconsolidated investments	98,935	105,415	80,790
Other, net	1,643	312	21,401
Total other expenses, net	(118,654)	(110,938)	(94,609)
Earnings from continuing operations before income taxes	359,204	349,677	251,480
Federal and state income tax expense	103,780	107,029	71,900
Earnings from continuing operations	255,424	242,648	179,580
Loss from discontinued operations	0	(18,100)	0
Net earnings	255,424	224,548	179,580
Preferred stock dividends	0	(5,040)	(8,683)
Loss on extinguishment of preferred stock	0	(3,295)	0
Net earnings available for common stockholders	$ 255,424	$ 216,213	$ 170,897
Net earnings available for common stockholders from continuing operations per share:
Basic	$ 2.05	$ 1.88	$ 1.38
Diluted	$ 2.02	$ 1.87	$ 1.37
Net earnings available for common stockholders per share:
Basic	$ 2.05	$ 1.74	$ 1.38
Diluted	$ 2.02	$ 1.73	$ 1.37
Cash dividends declared on common stock per share:	$ 0.60	$ 0.60	$ 0.60
Weighted average shares outstanding:
Basic	124,720	124,474	124,076
Diluted	126,283	125,191	124,409