Segment Information (Company's Segment Information, Assets) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total assets	$ 5,307,181	$ 5,051,817
Regulated Assets [Member]
Segment Reporting Information [Line Items]
Total assets	5,146,961	4,893,573
Other Assets [Member]
Segment Reporting Information [Line Items]
Total assets	$ 160,220	$ 158,244