Other Comprehensive Income: Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense									$ 73,017	$ 113,979	$ 117,754
Revenue	378,077	272,087	283,237	460,169	355,448	259,907	279,826	380,671	1,393,570	1,275,852	1,173,884
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes									194,177	177,540	136,895
Utilities - Operations and maintenance									270,954	261,919	242,367
Non-regulated energy operations and maintenance									88,141	83,762	85,830
Income tax benefit (expense)									(65,395)	(61,608)	(48,400)
Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes									5,664	6,062
Income tax benefit (expense)									(2,344)	(2,016)
Net income (loss) available for common stock									3,320	4,046
Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense									3,669	6,989
Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income [Member] | Commodity Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenue									1,995	(927)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Utilities - Operations and maintenance									(102)	(125)
Non-regulated energy operations and maintenance									(115)	(128)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Utilities - Operations and maintenance									630	1,693
Non-regulated energy operations and maintenance									364	1,098
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes									777	2,538
Income tax benefit (expense)									(272)	(883)
Net income (loss) available for common stock									$ 505	$ 1,655