Taxes Other Than Income Taxes (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Total taxes other than income	$ 13,446	$ 12,943	$ 27,211	$ 25,803
Property [Member]
Total taxes other than income	6,781	6,513	13,852	13,039
Capital Stock [Member]
Total taxes other than income	892	924	1,773	1,791
Gross Receipts, Excise and Franchise [Member]
Total taxes other than income	2,620	2,459	4,937	4,680
Payroll [Member]
Total taxes other than income	1,621	1,600	3,940	3,748
Other [Member]
Total taxes other than income	$ 1,532	$ 1,447	$ 2,709	$ 2,545