Subsequent Events (Details) (USD $)	0 Months Ended		1 Months Ended		3 Months Ended
	Feb. 28, 2012	Jan. 05, 2012	Mar. 31, 2012	Feb. 29, 2012	Mar. 21, 2012
Subsequent Events Details [Abstract]
Short-term Debt, Terms			$650 million unsecured CP program. The notes issued under the CP program will have maturities not to exceed 397 days from the date of issuance and will be backstopped by our existing $650 million revolving syndicated credit facility expiring January 25, 2014. The amount outstanding under the revolving syndicated credit facility and the CP program, either individually or in the aggregate, shall not exceed $650 million. Any borrowings under the CP program will rank equally with our other unsubordinated and unsecured debt.
Long-term Debt, Description				secured pricing confirmations from lenders that price $300 million of private placement long-term debt with the transaction expected to close on March 27, 2012. We will be issuing $100 million on or around July 16, 2012 with an interest rate of 3.47%. On or around October 15, 2012, we will be issuing the remaining $200 million with an interest rate of 3.57%. Both issuances will mature in fifteen years on or about July 16, 2027. The blended interest rate for these debt issuances is 3.54%. These proceeds will be used for general corporate purposes, including the repayment of short-term debt incurred in part for funding of capital expenditures for power generation gas delivery service projects.
Accelerated Share Repurchases Settlement Payment Or Receipt	$ (500,000)
Stock Repurchased And Retired During Period Shares		800,000
Accelerated Share Repurchases Initial Price Paid Per Share		$ 33.77
Accelerated Share Repurchases Weighted Average Purchase Price Per Share Prior To Discount	$ 33.25
Accelerated Share Repurchases Discount On Weighted Average Purchase Price Per Share	$ 0.09				$ 0.09
Accelerated Share Repurchases Final Price Paid Per Share	$ 33.16