Reportable Segments 1 (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Operating revenues from external customers	$ 670,314	$ 617,211	$ 631,607	$ 746,822	$ 670,296	$ 487,527	$ 573,096	$ 758,994	$ 2,665,954	$ 2,489,913	$ 2,179,018
Depreciation and amortization									237,690	228,637	213,827
Earnings from unconsolidated investments									98,935	105,415	80,790
Other income (expense), net									1,643	312	21,401
Interest expense									219,232	216,665	196,800
Federal and state income tax expense									103,780	107,029	71,900
Loss from discontinued operations					(18,100)	0	0	0	0	(18,100)	0
Net earnings	76,957	58,032	59,773	60,662					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	76,957	58,032	59,773	60,662	55,868	36,632	69,424	54,289	255,424	216,213	170,897
Assets	8,270,859				8,238,543				8,270,859	8,238,543
Transportation And Storage [Member]
Segment Reporting Information [Line Items]
Operating revenues from external customers									803,650	769,450	749,161
Depreciation and amortization									128,011	123,009	113,648
Earnings from unconsolidated investments									97,775	99,991	75,205
Other income (expense), net									603	(87)	1,657
EBIT									480,775	458,273	411,935
Assets	5,288,967				5,224,992				5,288,967	5,224,992
Expenditures for long-lived assets									101,852	145,674	247,097
Gathering And Processing [Member]
Segment Reporting Information [Line Items]
Operating revenues from external customers									1,179,680	1,008,023	732,251
Depreciation and amortization									72,756	70,056	66,690
Earnings from unconsolidated investments									(248)	4,145	4,410
Other income (expense), net									138	362	(84)
EBIT									50,666	41,756	(40,470)
Assets	1,742,516				1,700,598				1,742,516	1,700,598
Expenditures for long-lived assets									113,864	95,577	70,221
Distribution [Member]
Segment Reporting Information [Line Items]
Operating revenues from external customers									666,650	698,513	692,904
Depreciation and amortization									33,445	32,544	31,269
Other income (expense), net									41	(307)	7,447
EBIT									55,364	63,692	67,302
Assets	1,075,253				1,135,352				1,075,253	1,135,352
Expenditures for long-lived assets									50,780	41,484	46,090
Total Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues from external customers									2,649,980	2,475,986	2,174,316
Depreciation and amortization									234,212	225,609	211,607
Other income (expense), net									782	(32)	9,020
EBIT									586,805	563,721	438,767
Assets	8,106,736				8,060,942				8,106,736	8,060,942
Expenditures for long-lived assets									266,496	282,735	363,408
Corporate And Other Activities [Member]
Segment Reporting Information [Line Items]
Operating revenues from external customers									15,974	13,927	4,702
Depreciation and amortization									3,478	3,028	2,220
Earnings from unconsolidated investments									1,408	1,279	1,175
Other income (expense), net									861	344	12,381
EBIT									(8,369)	2,621	9,513
Assets	164,123				177,601				164,123	177,601
Expenditures for long-lived assets									$ 2,491	$ 4,690	$ 30,141