Segment Information (Company's Segment Information, Assets) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Total assets	$ 4,228,069	$ 4,072,466
Regulated [Member] | Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Total assets	169,727	163,499
Regulated [Member]
Segment Reporting Information [Line Items]
Total assets	4,142,219	3,991,493
Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Total assets	$ 85,850	$ 80,973