Rate Matters (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 PSCW [Member]	Dec. 31, 2011 PSCW [Member]	Dec. 31, 2014 PSCW [Member] Approved Future Rate Matters [Member]	Dec. 31, 2013 PSCW [Member] Columbia Environmental Project [Member]	Dec. 31, 2012 PSCW [Member] Columbia Environmental Project [Member]	Dec. 31, 2011 PSCW [Member] Columbia Environmental Project [Member]	Dec. 31, 2014 PSCW [Member] Columbia Environmental Project [Member] Approved Future Rate Matters [Member]	Dec. 31, 2013 Electric Rate Proceeding [Member] PSCW [Member]	Dec. 31, 2012 Electric Rate Proceeding [Member] PSCW [Member]	Dec. 31, 2011 Electric Rate Proceeding [Member] PSCW [Member]	Dec. 31, 2014 Electric Rate Proceeding [Member] PSCW [Member] Approved Future Rate Matters [Member]	Dec. 31, 2013 Gas Rate Proceeding [Member] PSCW [Member]	Dec. 31, 2012 Gas Rate Proceeding [Member] PSCW [Member]	Dec. 31, 2011 Gas Rate Proceeding [Member] PSCW [Member]	Dec. 31, 2014 Gas Rate Proceeding [Member] PSCW [Member] Approved Future Rate Matters [Member]
Public Utilities, Rate Matters [Abstract]
Authorized rate increase (decrease), percentage											3.80%	4.30%	2.30%	0.00%	1.00%	0.30%	1.00%	0.00%
Authorized rate increase (decrease), amount											$ 14.9	$ 15.7	$ 8.0	$ 0	$ 1.6	$ 0.6	$ 1.9	$ 0
Authorized AFUDC rate	50.00%	50.00%	50.00%				50.00%	100.00%	100.00%	100.00%
Return of fuel rule surplus credit, to be amortized						6.2
Authorized return on common stock				10.30%	10.30%	10.30%
Approved equity capital structure, percentage					58.10%
Fuel Rules [Abstract]
Fuel rules, bandwidth				2.00%	2.00%
Fuel rules, electric fuel costs, deferral, upper threshold	102.00%
Fuel rules, electric fuel costs, deferral, lower threshold	98.00%
Fuel rules, deferred electric cost	$ (6.7)