CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
OPERATING ACTIVITIES
Net (loss) income	$ 45.5	$ (3.7)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	240.2	254.2
Deferred income taxes	20.7	(9.3)
Impairment	2.0	0
Share-based compensation	6.8	6.1
Amortization of debt issuance costs and discounts	1.7	1.5
Net gain from asset sales	(2.4)	0.2
Income from unconsolidated affiliates	(2.2)	(1.3)
Distributions from unconsolidated affiliates and other	2.7	1.5
Unrealized loss (gain) on derivative contracts	45.5	85.3
Changes in operating assets and liabilities	(38.1)	(162.4)
Net Cash Provided by Operating Activities	322.4	172.1
INVESTING ACTIVITIES
Property acquisitions	(946.6)	(23.6)
Property, plant and equipment, including dry exploratory well expense	(330.2)	(361.0)
Proceeds from disposition of assets	2.9	1.5
Escrow Deposit Disbursements Related to Property Acquisition	50.0	0
Net Cash Used in Investing Activities	(1,223.9)	(383.1)
FINANCING ACTIVITIES
Checks outstanding in excess of cash balances	(12.5)	60.0
Long-term debt issued	300.0	0
Long-term debt issuance costs paid	(1.1)	0
Proceeds from credit facility	1,643.0	1,027.0
Repayments of credit facility	(1,021.5)	(866.5)
Payments for Repurchase of Common Stock	(5.5)	(7.5)
Other capital contributions	2.9	2.1
Dividends paid	(3.6)	(3.6)
Excess tax benefit on share-based compensation	(0.6)	1.0
Distribution to noncontrolling interest	(7.6)	(1.5)
Net Cash Provided by Financing Activities	893.5	211.0
Change in cash and cash equivalents	(8.0)	0
Beginning cash and cash equivalents	11.9	0
Ending cash and cash equivalents	3.9	0
Supplemental Disclosures:
Cash paid for interest, net of capitalized interest	43.8	40.7
Cash paid (received) for income taxes	0	4.9
Non-cash investing activities
Change in capital expenditure accrual balance	$ (11.6)	$ 42.6