Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating revenues:
Electric, natural gas distribution and regulated pipeline and midstream		$ 1,141,454	$ 1,149,038	$ 1,246,903
Nonregulated pipeline and midstream, construction materials and contracting, construction services and other		2,987,374	2,865,014	2,868,170
Total operating revenues		4,128,828	4,014,052	4,115,073
Operating expenses:
Fuel and purchased power		75,512	86,238	89,312
Purchased natural gas sold		382,753	450,114	558,463
Operation and maintenance:
Electric, natural gas distribution and regulated pipeline and midstream		312,404	278,171	269,175
Nonregulated pipeline and midstream, construction materials and contracting, construction services and other		2,580,895	2,527,052	2,523,039
Depreciation, depletion and amortization		216,318	211,747	203,084
Taxes, other than income		151,826	140,955	144,818
Total operating expenses		3,719,708	3,694,277	3,787,891
Operating income		409,120	319,775	327,182
Other income		4,956	18,457	9,138
Interest expense		87,848	91,179	86,871
Income before income taxes		326,228	247,053	249,449
Income taxes		93,132	70,664	64,422
Income from continuing operations		233,096	176,389	185,027
Income (loss) from discontinued operations, net of tax (Note 2)	[1]	(300,354)	(834,080)	109,311
Net income (loss)		(67,258)	(657,691)	294,338
Loss from discontinued operations attributable to noncontrolling interest (Note 2)		(131,691)	(35,256)	(3,895)
Dividends declared on preferred stocks		685	685	685
Earnings (loss) on common stock		$ 63,748	$ (623,120)	$ 297,548
Earnings (loss) per common share - basic:
Earnings before discontinued operations		$ 1.19	$ 0.90	$ 0.96
Discontinued operations attributable to the Company, net of tax		(0.86)	(4.10)	0.59
Earnings (loss) per common share - basic		0.33	(3.20)	1.55
Earnings (loss) per common share - diluted:
Earnings before discontinued operations		1.19	0.90	0.96
Discontinued operations attributable to the Company, net of tax		(0.86)	(4.10)	0.59
Earnings (loss) per common share - diluted		$ 0.33	$ (3.20)	$ 1.55
Weighted average common shares outstanding - basic		195,299	194,928	192,507
Weighted average common shares outstanding - diluted		195,618	194,986	192,587

[1] Includes eliminations for the presentation of income tax adjustments between continuing and discontinued operations.