CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current Assets
Cash and cash equivalents	$ 146.4	$ 0
Accounts receivable, net	236.9	397.4
Fair value of derivative contracts	268.2	273.7
Inventories, at lower of average cost or market
Gas, oil and NGL	11.6	16.2
Materials and supplies	90.0	87.6
Prepaid expenses and other	42.5	43.7
Total Current Assets	795.6	818.6
Property, Plant and Equipment (successful efforts method for gas and oil properties)
Proved properties	8,822.3	8,172.4
Unproved properties	305.4	326.8
Midstream field services	1,550.1	1,463.6
Marketing and other	53.6	49.8
Total Property, Plant and Equipment	10,731.4	10,012.6
Less Accumulated Depreciation, Depletion and Amortization
Exploration and production	3,763.7	3,339.2
Midstream field services	327.8	297.5
Marketing and other	16.3	14.6
Total Accumulated Depreciation, Depletion and Amortization	4,107.8	3,651.3
Net Property, Plant and Equipment	6,623.6	6,361.3
Investment in unconsolidated affiliates	41.9	42.2
Goodwill	59.5	59.5
Fair value of derivative contracts	76.2	123.5
Other noncurrent assets	40.8	37.6
TOTAL ASSETS	7,637.6	7,442.7
Current Liabilities
Checks outstanding in excess of cash balances	0	29.4
Accounts payable and accrued expenses	373.8	457.3
Production and property taxes	47.2	40.0
Interest payable	33.0	24.4
Fair value of derivative contracts	2.3	1.3
Deferred income taxes	31.0	85.4
Total Current Liabilities	487.3	637.8
Long-term debt	1,866.6	1,679.4
Deferred income taxes	1,563.1	1,484.7
Asset retirement obligations	172.2	163.9
Fair value of derivative contracts	2.4	0
Other long-term liabilities	129.8	124.8
Commitments and contingencies
EQUITY
Common stock - par value $0.01 per share; 500.0 million shares authorized; 178.5 million and 177.2 million shares issued, respectively	1.8	1.8
Treasury stock - 0.7 million and 0.4 million shares, respectively	(24.0)	(13.1)
Additional paid-in capital	450.4	431.4
Retained earnings	2,820.7	2,673.5
Accumulated other comprehensive income	118.1	207.9
Total Common Shareholders' Equity	3,367.0	3,301.5
Noncontrolling interest	49.2	50.6
Total Equity	3,416.2	3,352.1
TOTAL LIABILITIES AND EQUITY	$ 7,637.6	$ 7,442.7