Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 309,889	$ 1,272
Accounts receivable, net	76,119	63,097
Inventories	12,596	11,255
Assets held for sale	176,914	93,739
Derivative instruments	3,235	56,963
Prepayments and other	7,087	20,014
Total current assets	585,840	246,340
Oil and natural gas properties, successful efforts method
Proved properties	7,288,899	7,611,118
Unproved properties	85,618	145,724
Less accumulated depreciation, depletion and amortization	3,515,599	3,454,510
Oil and natural gas properties, net	3,858,918	4,302,332
Other property and equipment, net	45,755	48,358
Total property, plant and equipment, net	3,904,673	4,350,690
Other postretirement assets	4,358	3,881
Other assets	9,866	10,245
TOTAL ASSETS	4,504,737	4,611,156
Current Liabilities
Accounts payable	53,108	64,742
Accrued taxes	16,684	5,801
Accrued wages and benefits	13,386	28,563
Accrued capital costs	40,347	79,206
Revenue and royalty payable	57,979	60,493
Liabilities related to assets held for sale	13,279	12,789
Pension liabilities	0	15,685
Derivative instruments	46,452	459
Other	19,344	19,783
Total current liabilities	260,579	287,521
Long-term debt	551,245	773,550
Asset retirement obligations	91,473	89,990
Deferred income taxes	460,424	552,369
Noncurrent derivative instruments	12,875	0
Other long-term liabilities	11,910	11,866
Total liabilities	1,388,506	1,715,296
Commitments and Contingencies
Shareholders’ Equity
Preferred stock, cumulative, $0.01 par value, 5,000,000 shares authorized	0	0
Common shareholders’ equity
Common stock, $0.01 par value; 150,000,000 shares authorized; 100,130,219 shares and 81,770,161 shares issued at June 30, 2016 and December 31, 2015, respectively	1,001	818
Premium on capital stock	1,366,280	979,030
Retained earnings	1,879,659	2,046,016
Accumulated other comprehensive income (loss), net of tax
Pension and postretirement plans	1,995	263
Deferred compensation plan	2,235	1,965
Treasury stock, at cost; 3,122,699 shares and 3,026,350 shares at June 30, 2016 and December 31, 2015, respectively	(134,939)	(132,232)
Total shareholders’ equity	3,116,231	2,895,860
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 4,504,737	$ 4,611,156