Regulation and Rates (Details) (USD $) In Millions, unless otherwise specified	11 Months Ended										12 Months Ended
	Dec. 31, 2013 Subsidiaries [Member]	Jul. 02, 2013 Subsidiaries [Member]	Jan. 02, 2014 Decoupling Mechanism [Member] Electric [Member]	Jan. 02, 2014 Decoupling Mechanism [Member] Natural Gas [Member]	Jul. 02, 2013 Decoupling Mechanism [Member] Subsidiaries [Member] Electric [Member]	Jul. 02, 2013 Decoupling Mechanism [Member] Subsidiaries [Member] Natural Gas [Member]	Jul. 02, 2013 Expedited Rate Filing [Member] Subsidiaries [Member] Electric [Member]	Jul. 02, 2013 Expedited Rate Filing [Member] Subsidiaries [Member] Natural Gas [Member]	Nov. 01, 2013 Power Cost Only Rate Case (PCORC) [Member] Subsidiaries [Member] Electric [Member]	Nov. 01, 2013 Purchased Gas Adjustment (PGA) [Member] Subsidiaries [Member] Natural Gas [Member]	Dec. 31, 2014 Scenario, Forecast [Member] Subsidiaries [Member]	May 01, 2014 Subsequent Event [Member] Decoupling Mechanism [Member] Subsidiaries [Member] Electric [Member]	May 01, 2014 Subsequent Event [Member] Decoupling Mechanism [Member] Subsidiaries [Member] Natural Gas [Member]	May 01, 2014 Subsequent Event [Member] Property tax tracker [Member] [Domain] [Domain] Subsidiaries [Member] Electric [Member]	May 01, 2014 Subsequent Event [Member] Property tax tracker [Member] [Domain] [Domain] Subsidiaries [Member] Natural Gas [Member]
Regulatory Assets [Line Items]
American Recovery and Reinvestment Tax Act of 2009, Grant Amortization Period	10 years
American Recovery and Reinvestment Tax Act of 2009, Grant, Amortization Period Included in Customer Pass Through	11 months
American Recovery and Reinvestment Tax Act of 2009, Grant Pass Through Amount	$ 34.6										$ 37.8
American Recovery and Reinvestment Tax Act of 2009, Grant Pass Through Interest Amount	23.8										20.6
American Recovery and Reinvestment Tax Act of 2009, Grant, Overall Average Rate Reduction	2.76%										(0.26%)
American Recovery and Reinvestment Tax Act of 2009, Total Grant Pass Through Amount											58.5
Public Utilities, Rate Case, Approved Effective Annual Rate Increase (Decrease)					$ 21.4	$ 10.8	$ 30.7	$ (2.0)	$ (10.5)	$ 4.0		$ 10.6	$ (1.0)	$ 11.0	$ 5.6
Public Utilities, Rate Case, Approved Effective Annual Rate Percentage Increase (Decrease)			3.00%	2.20%	1.00%	1.10%	1.50%	(0.20%)	(0.50%)	0.40%		0.50%	(0.10%)	0.50%	0.60%
Rate Case, Approved Effective Weighted Cost of Capital		7.77%
Rate Case, Approved Effective Common Equity in Capital Structure		48.00%
Rate Case, Approved Effective Return on Equity		9.80%