CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 72.0	$ 27.4
Collateral on deposit	25.4	41.0
Accounts receivable and accrued unbilled revenues, net of reserves of $47.2 and $43.5, respectively	899.0	796.8
Inventories	140.2	271.9
Assets from risk management activities	182.5	145.4
Regulatory assets	88.4	110.8
Assets held for sale	2.5	10.1
Deferred income taxes	42.8	64.3
Prepaid taxes	116.6	152.8
Other current assets	31.3	38.6
Current assets	1,600.7	1,659.1
Property, plant, and equipment, net of accumulated depreciation of $3,225.5 and $3,114.7, respectively	5,941.8	5,501.9
Regulatory assets	1,842.7	1,813.8
Assets from risk management activities	50.3	45.3
Equity method investments	518.3	512.2
Goodwill	658.3	658.3
Other long-term assets	152.3	136.8
Total assets	10,764.4	10,327.4
Liabilities and Equity
Short-term debt	756.4	482.4
Current portion of long-term debt	291.5	313.5
Accounts payable	450.1	457.7
Liabilities from risk management activities	140.9	181.9
Accrued taxes	95.9	83.0
Regulatory liabilities	84.8	65.6
Liabilities held for sale		0.2
Other current liabilities	287.1	229.0
Current liabilities	2,106.7	1,813.3
Long-term debt	1,931.7	1,931.7
Deferred income taxes	1,263.9	1,203.8
Deferred investment tax credits	48.9	49.3
Regulatory liabilities	377.6	370.5
Environmental remediation liabilities	641.2	651.5
Pension and other postretirement benefit obligations	566.4	625.2
Liabilities from risk management activities	49.3	58.4
Asset retirement obligations	416.3	411.2
Other long-term liabilities	138.3	135.7
Long-term liabilities	5,433.6	5,437.3
Commitments and contingencies
Common stock - $1 par value; 200,000,000 shares authorized; 78,809,948 shares issued; 78,353,096 shares outstanding	78.8	78.3
Additional paid-in capital	2,590.2	2,574.6
Retained earnings	565.4	431.5
Accumulated other comprehensive loss	(39.3)	(40.9)
Shares in deferred compensation trust	(22.0)	(17.7)
Total common shareholders' equity	3,173.1	3,025.8
Preferred stock of subsidiary - $100 par value; 1,000,000 shares authorized; 511,882 shares issued; 510,495 shares outstanding	51.1	51.1
Noncontrolling interest in subsidiaries	(0.1)	(0.1)
Total liabilities and equity	$ 10,764.4	$ 10,327.4