CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OPERATING ACTIVITIES
NET INCOME	$ 132.0	$ 270.4	$ 329.1
Discontinued operations, net of income tax	0	0	43.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	904.9	765.4	643.4
Deferred income taxes	32.1	156.8	188.2
Abandonment and impairment	133.4	218.4	46.1
Share-based compensation	25.6	22.0	16.1
Amortization of debt issuance costs and discounts	5.3	4.1	2.4
Net gain from asset sales	(1.2)	(1.4)	(12.1)
Income from unconsolidated affiliates	(6.8)	(5.5)	(3.0)
Distributions from unconsolidated affiliates and dry exploratory well expense	7.9	8.1	11.8
Non-cash loss on early extinguishment of debt	0	0.7	13.3
Unrealized gain on derivative contracts	(63.2)	(117.7)	(121.7)
Changes in operating assets and liabilities
Accounts receivable	9.6	(144.6)	(32.6)
Inventories	28.7	(22.0)	10.1
Prepaid expenses	(16.8)	1.6	(16.2)
Accounts payable and accrued expenses	101.3	127.8	4.2
Federal income taxes	3.5	17.0	(30.9)
Other	(0.3)	(8.5)	(7.5)
Net Cash Provided by Operating Activities of Continuing Operations	1,296.0	1,292.6	997.5
INVESTING ACTIVITIES
Property acquisitions	(1,401.0)	(48.0)	(109.3)
Property, plant and equipment, including dry exploratory well expense	(1,398.7)	(1,383.1)	(1,359.7)
Proceeds from disposition of assets	5.2	8.2	25.6
Change in notes receivable	0	0	52.9
Net Cash Used in Investing Activities of Continuing Operations	(2,794.5)	(1,422.9)	(1,390.5)
FINANCING ACTIVITIES
Checks outstanding in excess of cash balances	10.3	9.9	19.5
Long-term debt issued	1,450.0	0	1,034.4
Long-term debt issuance costs paid	(17.8)	(10.6)	(16.6)
Long-term debt repaid	(6.7)	(58.5)	(91.5)
Repayments of notes payable	0	0	(39.3)
Long-term debt extinguishment costs	0	0	(4.9)
Proceeds from credit facility	1,234.5	591.5	0
Repayments of credit facility	(1,151.0)	(385.0)	(761.5)
Other capital contributions	(2.2)	0.7	2.8
Equity contribution	0	0	250.0
Dividends paid	(14.2)	(14.1)	(7.0)
Dividends	(14.2)	(14.1)	(15.9)
Excess tax benefit on share-based compensation	2.2	1.6	0
Distribution from Questar	0	0.2	(7.2)
Distribution to noncontrolling interest	(6.6)	(5.4)	(5.0)
Net Cash Provided by Financing Activities of Continuing Operations	1,498.5	130.3	373.7
CASH USED IN CONTINUING OPERATIONS	0	0	(19.3)
Cash provided by operating activities of discontinued operations	0	0	68.6
Cash used in investing activities of discontinued operations	0	0	(39.9)
Cash used in financing activities of discontinued operations	0	0	(26.9)
Effect of change in cash and cash equivalents of discontinued operations	0	0	1.8
Change in cash and cash equivalents	0	0	(19.3)
Beginning cash and cash equivalents	0	0	19.3
Ending cash and cash equivalents	$ 0	$ 0	$ 0