Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Operating activities
Net income	$ 70.1	$ 98.3
Adjustments to reconcile net income to net cash flow provided from operating activities:
Depreciation	155.4	151.9
Deferred income tax expense (benefit)	2.0	(9.9)
Changes in assets and liabilities:
Receivables, less allowances	241.1	256.4
Gas in storage	(76.3)	(90.6)
Deferred/accrued gas costs	(9.2)	6.9
Derivative instruments	(9.1)	6.6
Margin accounts - derivative instruments	33.5	(1.7)
Other assets	(9.7)	23.2
Accounts payable	(39.6)	(68.1)
Customer credit balances and deposits	(1.3)	(10.5)
Other liabilities	20.1	(6.3)
Other items	(11.9)	(8.4)
Net cash flow provided from operating activities	365.1	347.8
Investing activities
Additions to property, plant & equipment	(190.5)	(148.7)
Purchases of held-to-maturity securities	0	(8.0)
Net decrease in other short-term investments	20.0	10.8
Other investing activities	(1.5)	(1.6)
Net cash flow used for investing activities	(172.0)	(147.5)
Financing activities
Proceeds from issuing long-term debt	75.0	0
Disbursements to retire long-term debt	(75.0)	0
Net repayments of commercial paper	(112.4)	(120.7)
Debt issuance costs	(1.5)	(5.8)
Dividends paid	(64.0)	(63.8)
Repurchases of common stock	(11.1)	(0.3)
Proceeds from exercise of stock options	5.9	9.0
Other financing activities	0.1	0.7
Net cash flow used for financing activities	(183.0)	(180.9)
Net increase in cash and cash equivalents	10.1	19.4
Cash and cash equivalents, beginning of period	31.5	55.7
Cash and cash equivalents, end of period	$ 41.6	$ 75.1