CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 0.0	$ 0.0
Accounts receivable, net	130.2	142.1
Income tax receivable	4.7	4.9
Fair value of derivative contracts	3.2	3.4
Hydrocarbon inventories, at lower of average cost or net realizable value	2.1	3.6
Prepaid expenses	9.4	10.7
Other current assets	0.2	0.7
Total Current Assets	149.8	165.4
Property, Plant and Equipment (successful efforts method for oil and gas properties)
Proved properties	12,676.1	12,470.9
Unproved properties	1,073.7	1,095.8
Gathering and other	383.4	319.7
Materials and supplies	38.4	37.8
Total Property, Plant and Equipment	14,171.6	13,924.2
Less Accumulated Depreciation, Depletion and Amortization
Exploration and production	6,660.8	6,642.9
Gathering and other	130.6	124.3
Total Accumulated Depreciation, Depletion and Amortization	6,791.4	6,767.2
Net Property, Plant and Equipment	7,380.2	7,157.0
Fair value of derivative contracts	4.5	0.1
Other noncurrent assets	74.1	72.3
TOTAL ASSETS	7,608.6	7,394.8
Current Liabilities
Checks outstanding in excess of cash balances	19.8	44.0
Accounts payable	400.9	364.6
Production and property taxes	31.9	31.6
Interest payable	33.4	26.0
Fair value of derivative contracts	116.9	103.6
Other current liabilities	10.1	7.5
Total Current Liabilities	613.0	577.3
Long-term debt	2,458.1	2,160.8
Deferred income taxes	504.0	518.0
Asset retirement obligations	200.4	206.6
Fair value of derivative contracts	32.8	31.8
Other long-term liabilities	103.6	102.4
Commitments and contingencies (Note 10)
EQUITY
Common stock – par value $0.01 per share; 500.0 million shares authorized; 240.3 million and 243.0 million shares issued, respectively	2.4	2.4
Treasury stock – 2.6 million and 2.0 million shares, respectively	(39.5)	(34.2)
Additional paid-in capital	1,408.0	1,398.2
Retained earnings	2,336.3	2,442.6
Accumulated other comprehensive income (loss)	(10.5)	(11.1)
Total Common Shareholders' Equity	3,696.7	3,797.9
TOTAL LIABILITIES AND EQUITY	$ 7,608.6	$ 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.