Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 447,925	$ 1,272
Accounts receivable, net	72,587	63,097
Inventories	14,159	11,255
Assets held for sale	0	93,739
Derivative instruments	3,653	56,963
Prepayments and other	6,240	20,014
Total current assets	544,564	246,340
Oil and natural gas properties, successful efforts method
Proved properties	7,394,628	7,611,118
Unproved properties	193,074	145,724
Less accumulated depreciation, depletion and amortization	3,622,344	3,454,510
Oil and natural gas properties, net	3,965,358	4,302,332
Other property and equipment, net	45,198	48,358
Total property, plant and equipment, net	4,010,556	4,350,690
Other postretirement assets	4,350	3,881
Other assets	9,654	10,245
TOTAL ASSETS	4,569,124	4,611,156
Current Liabilities
Long-term debt due within one year	19,000	0
Accounts payable	56,221	64,742
Accrued taxes	35,071	5,801
Accrued wages and benefits	20,000	28,563
Accrued capital costs	56,858	79,206
Revenue and royalty payable	52,241	60,493
Liabilities related to assets held for sale	0	12,789
Pension liabilities	0	15,685
Derivative instruments	24,909	459
Other	14,421	19,783
Total current liabilities	278,721	287,521
Long-term debt	532,343	773,550
Asset retirement obligations	92,937	89,990
Deferred income taxes	475,239	552,369
Noncurrent derivative instruments	6,043	0
Other long-term liabilities	11,714	11,866
Total liabilities	1,396,997	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; 100,134,145 shares and 81,770,161 shares issued at September 30, 2016 and December 31, 2015, respectively	1,001	818
Premium on capital stock	1,369,045	979,030
Retained earnings	1,932,973	2,046,016
Accumulated other comprehensive income (loss), net of tax
Pension and postretirement plans	1,925	263
Deferred compensation plan	2,221	1,965
Treasury stock, at cost; 3,123,971 shares and 3,026,350 shares at September 30, 2016 and December 31, 2015, respectively	(135,038)	(132,232)
Total shareholders’ equity	3,172,127	2,895,860
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 4,569,124	$ 4,611,156