CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 178.8	$ 443.8
Accounts receivable, net	165.0	155.7
Income tax receivable	12.9	18.6
Fair value of derivative contracts	48.8	0.0
Hydrocarbon inventories, at lower of average cost or market	8.6	10.4
Prepaid expenses and other	10.2	11.6
Total Current Assets	424.3	640.1
Property, Plant and Equipment (successful efforts method for gas and oil properties)
Proved properties	14,840.2	14,232.5
Unproved properties	729.6	871.5
Gathering and other	305.8	301.8
Material and supplies	39.0	32.7
Total Property, Plant and Equipment	15,914.6	15,438.5
Less Accumulated Depreciation, Depletion and Amortization
Exploration and production	9,069.9	8,797.7
Gathering and other	107.4	101.8
Total Accumulated Depreciation, Depletion and Amortization	9,177.3	8,899.5
Net Property, Plant and Equipment	6,737.3	6,539.0
Fair value of derivative contracts	28.6	0.0
Other noncurrent assets	75.3	66.3
TOTAL ASSETS	7,265.5	7,245.4
Current Liabilities
Checks outstanding in excess of cash balances	11.9	12.3
Accounts payable and accrued expenses	305.9	269.7
Production and property taxes	33.0	30.1
Interest payable	32.9	32.9
Fair value of derivative contracts	1.4	169.8
Current portion of long-term debt	134.0	0.0
Total Current Liabilities	519.1	514.8
Long-term debt	1,889.0	2,020.9
Deferred income taxes	894.3	825.9
Asset retirement obligations	225.6	225.8
Fair value of derivative contracts	0.1	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; 242.2 million and 240.7 million shares issued, respectively	2.4	2.4
Treasury stock – 1.7 million and 1.1 million shares, respectively	(30.3)	(22.9)
Additional paid-in capital	1,382.1	1,366.6
Retained earnings	2,295.6	2,173.3
Accumulated other comprehensive income (loss)	(14.8)	(16.7)
Total Shareholders' Equity	3,635.0	3,502.7
TOTAL LIABILITIES AND EQUITY	$ 7,265.5	$ 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.