Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income	$ 214	$ 174
Adjustments to reconcile net income to net cash flow provided by operating activities
Depreciation and amortization	216	206
Change in derivative instrument assets and liabilities	14	18
Deferred income taxes	(18)	56
Gain on sale of Compass Energy	(11)
Changes in certain assets and liabilities
Receivables, other than energy marketing	267	367
Inventories, net of temporary LIFO liquidation	262	242
Energy marketing receivables and trade payables, net	86	53
Prepaid taxes	57	33
Accrued natural gas costs	40	20
Trade payables, other than energy marketing	(15)	(34)
Other - net	49	(45)
Net cash flow provided by operating activities	1,161	1,090
Cash flows from investing activities
Expenditures for property, plant and equipment	(318)	(350)
Acquisitions of assets	(122)
Disposition of assets	12
Other	15	(8)
Net cash flow used in investing activities	(413)	(358)
Cash flows from financing activities
Issuance of senior notes	494
Net payments and borrowings of short-term debt	(857)	(590)
Payment of senior notes	(225)
Dividends paid on common shares	(111)	(96)
Distribution to noncontrolling interest	(17)	(14)
Other	21	(14)
Net cash flow used in financing activities	(695)	(714)
Net increase in cash and cash equivalents	53	18
Cash and cash equivalents at beginning of period	131	69
Cash and cash equivalents at end of period	184	87
Cash paid during the period for
Interest	89	86
Income taxes	60	4
Non cash financing transaction
Refinancing of gas facility revenue bonds	$ 200