Regulatory Matters (Details Textuals 1) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Mar. 31, 2011	Sep. 30, 2011 percent people years kWh Days weeks MCF banks customers ratio employees
Regulatory Assets and Liability [Line Items]
MPSC Authorized Recovery of Uncollectibe Expense	$ 31
Uncollectibe Expense Prior Year		7
Uncollectible Expense Tracking Mechanism Under Collection Three Years Prior		24
Requested Recovery for Revenue Decoupling Mechanism		20
GCR Plan Case Factory Current Year and Next Year		5.89
Gas Main Renewal Program Implentation Time Period		10
Gas Main Renewal Program Capital Expenditures		17
Gas Meter Move Out Program Implementation Time Period		10
Gas Meter Move Out Program Capital Expenditures		$ 22