Segment Information (Company's Segment Information, Assets) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Total assets	$ 4,420,247	$ 4,348,420
Regulated [Member]
Segment Reporting Information [Line Items]
Total assets	4,211,877	4,186,639
Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Total assets	208,370	161,781
Discontinued Operations [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Total assets	$ 504	$ 172,238