Selected Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2012

Selected Quarterly Financial Data [Abstract]

Selected Quarterly Financial Data

		First		Second		Third		Fourth
		Quarter		Quarter		Quarter		Quarter		Year
2012
Operating revenues	$	164,024	$	191,690	$	214,565	$	187,481	$	757,760
Operations and maintenance expense		64,825		63,571		71,268		72,179		271,843
Operating income		61,839		87,032		100,535		72,111		321,517
Income from continuing operations		26,889		41,780		50,284		65,134		184,087
Income/(loss) from discontinuing operations		11,015		(335)		375		1,421		12,476
Net income attributable to common shareholders		37,904		41,445		50,659		66,555		196,563
Basic income from continuing operations per common share		0.19		0.30		0.36		0.47		1.32
Diluted income from continuing operations per common share		0.19		0.30		0.36		0.46		1.32
Basic income (loss) from discontinued operations per common share		0.08		(0.00)		0.00		0.01		0.09
Diluted  income (loss) from discontinued operations per common share		0.08		(0.00)		0.00		0.01		0.09
Basic net income per common share		0.27		0.30		0.36		0.48		1.41
Diluted net income per common share		0.27		0.30		0.36		0.47		1.40
Dividend paid per common share		0.165		0.165		0.165		0.175		0.670
Dividend declared per common share		0.165		0.165		0.340		-		0.670
Price range of common stock
- high		22.75		25.17		26.93		25.94		26.93
- low		21.06		21.52		24.06		24.15		21.06
2011
Operating revenues	$	157,576	$	171,839	$	191,083	$	166,793	$	687,291
Operations and maintenance expense		60,379		63,360		66,502		66,502		256,743
Operating income		59,216		71,222		86,702		63,659		280,799
Income from continuing operations		29,597		35,719		44,861		31,506		141,683
Income/(loss) from discontinuing operations		754		1,871		(3,738)		2,499		1,386
Net income attributable to common shareholders		30,351		37,590		41,123		34,005		143,069
Basic income from continuing operations per common share		0.21		0.26		0.32		0.23		1.03
Diluted income from continuing operations per common share		0.21		0.26		0.32		0.23		1.02
Basic income (loss) from discontinued operations per common share		0.01		0.01		(0.03)		0.02		0.01
Diluted  income (loss) from discontinued operations per common share		0.01		0.01		(0.03)		0.02		0.01
Basic net income per common share		0.22		0.27		0.30		0.25		1.04
Diluted net income per common share		0.22		0.27		0.30		0.24		1.03
Dividend paid per common share		0.155		0.155		0.155		0.165		0.630
Dividend declared per common share		0.155		0.155		0.320		-		0.630
Price range of common stock
- high		23.79		23.28		22.74		22.52		23.79
- low		21.56		21.03		19.28		20.16		19.28