CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
OPERATING ACTIVITIES
Net (loss) income	$ 154.1	$ 269.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	647.4	566.4
Deferred income taxes	54.7	155.9
Abandonment and impairment	71.8	16.4
Share-based compensation	19.5	16.5
Amortization of debt issuance costs and discounts	3.7	2.4
Dry exploratory well expense	0.1	0.5
Net gain from asset sales	(1.5)	(1.4)
Income from unconsolidated affiliates	(5.6)	(4.5)
Distributions from unconsolidated affiliates and other	6.1	7.6
Non-cash loss on early extinguishment of debt	0	0.7
Unrealized gain on derivative contracts	(32.8)	(86.7)
Changes in operating assets and liabilities	54.5	12.2
Net Cash Provided by Operating Activities	972.0	955.7
INVESTING ACTIVITIES
Property acquisitions	(1,400.3)	(40.7)
Property, plant and equipment, including dry exploratory well expense	(1,040.7)	(957.7)
Proceeds from disposition of assets	5.3	7.4
Net Cash Used in Investing Activities	(2,435.7)	(991.0)
FINANCING ACTIVITIES
Checks outstanding in excess of cash balances	(1.9)	7.2
Long-term debt issued	1,450.0	0
Long-term debt issuance costs paid	(17.0)	(10.5)
Long-term debt repaid	(6.7)	(58.5)
Proceeds from credit facility	933.5	280.0
Repayments of credit facility	(876.0)	(170.0)
Other capital contributions	(4.2)	0.1
Dividends paid	(10.7)	(10.6)
Excess tax benefit on share-based compensation	2.0	1.5
Distribution from Questar	0	0.2
Distribution to noncontrolling interest	(5.3)	(4.1)
Net Cash Provided by Financing Activities	1,463.7	35.3
Change in cash and cash equivalents	0	0
Beginning cash and cash equivalents	0	0
Ending cash and cash equivalents	0	0
Supplemental Disclosures:
Cash paid for interest	81.9	89.8
Cash paid (received) for income taxes	28.0	(7.2)
Non-cash investing activities
Change in capital expenditure accrual balance	$ 97.5	$ 12.5