Changes in Operations (Details 4) (USD $) In Thousands, except Per Share data	3 Months Ended	6 Months Ended
	Jun. 30, 2010	Jun. 30, 2010
Business Combination Pro Forma Information [Line Items]
Operating revenues	$ 182,112	$ 347,842
Net income	$ 22,995	$ 39,793
Basic earnings per common share from continuing operations	$ 0.59	$ 1.03
Diluted earnings per common share from continuing operations	$ 0.55	$ 0.96