CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 0.0	$ 443.8
Accounts receivable, net	142.1	155.7
Income tax receivable	4.9	18.6
Fair value of derivative contracts	3.4	0.0
Hydrocarbon inventories, at lower of average cost or net realizable value	3.6	10.4
Prepaid expenses	10.7	11.4
Other current assets	0.7	0.2
Total Current Assets	165.4	640.1
Property, Plant and Equipment (successful efforts method for oil and gas properties)
Proved properties	12,470.9	14,232.5
Unproved properties	1,095.8	871.5
Gathering and other	319.7	301.8
Materials and supplies	37.8	32.7
Total Property, Plant and Equipment	13,924.2	15,438.5
Less Accumulated Depreciation, Depletion and Amortization
Exploration and production	6,642.9	8,797.7
Gathering and other	124.3	101.8
Total Accumulated Depreciation, Depletion and Amortization	6,767.2	8,899.5
Net Property, Plant and Equipment	7,157.0	6,539.0
Fair value of derivative contracts	0.1	0.0
Other noncurrent assets	72.3	66.3
TOTAL ASSETS	7,394.8	7,245.4
Current Liabilities
Checks outstanding in excess of cash balances	44.0	12.3
Accounts payable and accrued expenses	372.1	269.7
Production and property taxes	31.6	30.1
Interest payable	26.0	32.9
Fair value of derivative contracts	103.6	169.8
Total Current Liabilities	577.3	514.8
Long-term debt	2,160.8	2,020.9
Deferred income taxes	518.0	825.9
Asset retirement obligations	206.6	225.8
Fair value of derivative contracts	31.8	32.0
Other long-term liabilities	102.4	123.3
Commitments and Contingencies (Note 9)
EQUITY
Common stock - par value $0.01 per share; 500.0 million shares authorized; 243.0 million and 240.7 million shares issued, respectively	2.4	2.4
Treasury stock - 2.0 million and 1.1 million shares, respectively	(34.2)	(22.9)
Additional paid-in capital	1,398.2	1,366.6
Retained earnings	2,442.6	2,173.3
Accumulated other comprehensive income (loss)	(11.1)	(16.7)
Total Common Shareholders' Equity	3,797.9	3,502.7
TOTAL LIABILITIES AND EQUITY	$ 7,394.8	$ 7,245.4

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.