Segment Information (Tables)

12 Months Ended

Dec. 31, 2012

Segment Information [Abstract]

Company's Segment Information

				2012						2011
				Other and						Other and
		Regulated		Eliminations		Consolidated		Regulated		Eliminations		Consolidated
Operating revenues	$	740,030	$	17,730	$	757,760	$	674,927	$	12,364	$	687,291
Operations and maintenance expense		259,847		11,996		271,843		243,137		13,606		256,743
Depreciation		113,139		(1,372)		111,767		104,681		(1,269)		103,412
Operating income (loss)		316,602		4,915		321,517		282,587		(1,788)		280,799
Interest expense, net of AFUDC		67,433		6,182		73,615		64,990		5,664		70,654
Income tax		66,821		60		66,881		72,336		(3,225)		69,111
Income (loss) from continuing operations		182,769		1,318		184,087		145,493		(3,810)		141,683
Capital expenditures		346,676		1,309		347,985		324,433		1,375		325,808
Total assets		4,566,327		292,190		4,858,517		4,183,758		164,662		4,348,420
Goodwill		24,031		4,121		28,152		22,823		4,121		26,944
				2010
				Other and
		Regulated		Eliminations		Consolidated
Operating revenues	$	648,768	$	11,418	$	660,186
Operations and maintenance expense		238,093		12,896		250,989
Depreciation		101,644		(1,038)		100,606
Operating income (loss)		259,372		(2,038)		257,334
Interest expense, net of AFUDC		63,170		5,392		68,562
Income tax		77,318		(2,378)		74,940
Income (loss) from continuing operations		119,292		(2,913)		116,379
Capital expenditures		307,726		408		308,134
Total assets		3,986,819		85,647		4,072,466
Goodwill		23,797		4,121		27,918