Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating revenues:
Electric, natural gas distribution and regulated pipeline and midstream		$ 225,485	$ 206,052	$ 659,100	$ 591,918
Nonregulated pipeline and midstream, construction materials and contracting, construction services and other		842,154	837,896	1,346,465	1,312,245
Total operating revenues		1,067,639	1,043,948	2,005,565	1,904,163
Operating expenses:
Electric fuel and purchased power		16,752	15,914	38,638	37,925
Purchased natural gas sold		57,668	47,439	250,617	208,474
Operation and maintenance:
Electric, natural gas distribution and regulated pipeline and midstream		77,273	77,078	156,013	151,703
Nonregulated pipeline and midstream, construction materials and contracting, construction services and other		743,656	722,742	1,222,132	1,165,243
Depreciation, depletion and amortization		51,658	54,248	102,983	109,132
Taxes, other than income		40,953	37,562	88,391	80,736
Total operating expenses		987,960	954,983	1,858,774	1,753,213
Operating income		79,679	88,965	146,791	150,950
Other income		782	872	1,798	1,921
Interest expense		20,766	22,219	41,068	45,087
Income before income taxes		59,695	67,618	107,521	107,784
Income taxes		15,290	21,320	27,478	29,620
Income from continuing operations		44,405	46,298	80,043	78,164
Loss from discontinued operations, net of tax (Note 8)	[1]	(3,190)	(276,102)	(1,504)	(294,138)
Net income (loss)		41,215	(229,804)	78,539	(215,974)
Loss from discontinued operations attributable to noncontrolling interest (Note 8)		0	(120,651)	0	(131,691)
Loss on redemption of preferred stocks		600	0	600	0
Dividends declared on preferred stocks		0	171	171	343
Earnings (loss) on common stock		$ 40,615	$ (109,324)	$ 77,768	$ (84,626)
Earnings (loss) per common share - basic:
Earnings before discontinued operations		$ 0.22	$ 0.24	$ 0.41	$ 0.40
Discontinued operations attributable to the Company, net of tax		(0.01)	(0.80)	(0.01)	(0.83)
Earnings (loss) per common share - basic		0.21	(0.56)	0.40	(0.43)
Earnings (loss) per common share - diluted:
Earnings before discontinued operations		0.22	0.24	0.40	0.40
Discontinued operations attributable to the Company, net of tax		(0.01)	(0.80)	0.00	(0.83)
Earnings (loss) per common share - diluted		0.21	(0.56)	0.40	(0.43)
Dividends declared per common share		$ 0.1925	$ 0.1875	$ 0.3850	$ 0.3750
Weighted average common shares outstanding - basic		195,304	195,304	195,304	195,294
Weighted average common shares outstanding - diluted		195,973	195,699	195,993	195,678

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