Industry Segment Information (Tables)

12 Months Ended

Dec. 31, 2012

Segment Reporting [Abstract]

Schedule of segment information

Years ended December 31,(in thousands)	2012			2011			2010
Operating revenues
Oil and gas operations	$	1,165,580		$	948,526		$	958,762
Natural gas distribution	451,589			534,953			619,772
Total	$	1,617,169		$	1,483,479		$	1,578,534
Operating income (loss)
Oil and gas operations	$	367,243		$	363,131		$	406,729
Natural gas distribution	93,216			86,216			88,383
Eliminations and corporate expenses	(1,067		)	(1,078		)	(1,735		)
Total	$	459,392		$	448,269		$	493,377
Depreciation, depletion and amortization expense
Oil and gas operations	$	377,328		$	244,081		$	203,823
Natural gas distribution	42,270			39,916			44,042
Total	$	419,598		$	283,997		$	247,865
Interest expense
Oil and gas operations	$	49,972		$	30,907		$	25,753
Natural gas distribution	16,284			14,740			13,894
Eliminations and other	(700		)	(825		)	(425		)
Total	$	65,556		$	44,822		$	39,222
Income tax expense (benefit)
Oil and gas operations	$	114,375		$	120,079		$	138,775
Natural gas distribution	30,244			26,670			29,875
Other	(800		)	(1,048		)	(1,660		)
Total	$	143,819		$	145,701		$	166,990
Capital expenditures
Oil and gas operations	$	1,291,211		$	1,115,452		$	717,782
Natural gas distribution	71,869			73,984			93,566
Total	$	1,363,080		$	1,189,436		$	811,348
Identifiable assets
Oil and gas operations	$	4,975,170		$	4,046,242		$	3,160,601
Natural gas distribution	1,177,134			1,163,959			1,166,899
Eliminations and other	23,586			27,215			36,060
Total	$	6,175,890		$	5,237,416		$	4,363,560
Property, plant and equipment, net
Oil and gas operations	$	4,697,683		$	3,806,787		$	2,936,284
Natural gas distribution	842,685			813,471			782,665
Other	1,268			518			278
Total	$	5,541,636		$	4,620,776		$	3,719,227