CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 0.0	$ 0.0
Accounts receivable, net	191.7	141.8
Income tax receivable	4.1	4.9
Fair value of derivative contracts	14.0	3.4
Prepaid expenses	11.4	10.1
Other current assets	0.2	4.3
Total Current Assets	221.4	164.5
Property, Plant and Equipment (successful efforts method for oil and gas properties)
Proved properties	11,717.8	11,873.6
Unproved properties	1,034.4	1,086.4
Gathering and other	369.6	318.7
Materials and supplies	37.3	32.9
Total Property, Plant and Equipment	13,159.1	13,311.6
Less Accumulated Depreciation, Depletion and Amortization
Exploration and production	6,160.3	6,642.9
Gathering and other	121.4	124.3
Total Accumulated Depreciation, Depletion and Amortization	6,281.7	6,767.2
Net Property, Plant and Equipment	6,877.4	6,544.4
Fair value of derivative contracts	0.1	0.1
Other noncurrent assets	58.3	53.0
Noncurrent assets held for sale	0.0	632.8
TOTAL ASSETS	7,157.2	7,394.8
Current Liabilities
Checks outstanding in excess of cash balances	15.3	44.0
Accounts payable and accrued expenses	335.6	363.8
Production and property taxes	40.9	31.6
Interest payable	33.1	26.0
Fair value of derivative contracts	200.7	103.6
Asset retirement obligations	5.0	3.5
Total Current Liabilities	630.6	572.5
Long-term debt	2,451.1	2,160.8
Deferred income taxes	398.8	518.0
Asset retirement obligations	155.5	159.0
Fair value of derivative contracts	52.6	31.8
Other long-term liabilities	93.7	102.2
Other long-term liabilities held for sale	0.0	52.6
Commitments and contingencies (Note 10)
EQUITY
Common stock – par value $0.01 per share; 500.0 million shares authorized; 239.8 million and 243.0 million shares issued, respectively	2.4	2.4
Treasury stock – 3.0 million and 2.0 million shares, respectively	(44.2)	(34.2)
Additional paid-in capital	1,424.6	1,398.2
Retained earnings	2,002.0	2,442.6
Accumulated other comprehensive income (loss)	(9.9)	(11.1)
Total Common Shareholders' Equity	3,374.9	3,797.9
TOTAL LIABILITIES AND EQUITY	$ 7,157.2	$ 7,394.8

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

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- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.