Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 849,000	$ 893,000
Accounts receivable, net of allowance for doubtful accounts of $2,888 and $3,773 at June 30, 2017 and December 31, 2016, respectively	94,998,000	83,954,000
Materials and supplies	3,291,000	3,340,000
Current derivative asset (Note 10)	3,948,000	0
Current income tax receivable	114,000	99,000
Current deferred tax asset (Note 8)	0	25,211,000
Prepaid expenses and other	6,304,000	7,699,000
Total current assets	109,504,000	121,196,000
Oil and natural gas properties on the full cost method:
Proved properties	5,540,086,000	5,446,305,000
Unproved properties not being amortized	337,190,000	314,867,000
Drilling equipment	1,587,096,000	1,565,268,000
Gas gathering and processing equipment	711,355,000	705,859,000
Saltwater disposal systems	62,191,000	60,638,000
Corporate land and building	59,075,000	59,066,000
Transportation equipment	29,704,000	32,842,000
Other	52,799,000	48,590,000
Property, plant, and equipment, gross	8,379,496,000	8,233,435,000
Less accumulated depreciation, depletion, amortization, and impairment	6,044,966,000	5,952,330,000
Net property and equipment	2,334,530,000	2,281,105,000
Goodwill	62,808,000	62,808,000
Non-current derivative asset (Note 10)	689,000	377,000
Other assets	15,779,000	13,817,000
Total assets	2,523,310,000	2,479,303,000
Current liabilities:
Accounts payable	106,200,000	88,793,000
Accrued liabilities (Note 5)	39,092,000	39,651,000
Current derivative liability (Note 10)	1,036,000	21,564,000
Current portion of other long-term liabilities (Note 6)	14,593,000	14,907,000
Total current liabilities	160,921,000	164,915,000
Long-term debt less debt issuance costs (Note 6)	806,092,000	800,917,000
Non-current derivative liability (Note 10)	0	415,000
Other long-term liabilities (Note 6)	100,796,000	103,064,000
Deferred income taxes (Note 8)	211,038,000	215,922,000
Commitments and contingencies (Note 12)	0	0
Shareholders' equity:
Preferred stock, $1.00 par value, 5,000,000 shares authorized, none issued	0	0
Common stock, $.20 par value, 175,000,000 shares authorized, 52,889,118 and 51,494,318 shares issued as of June 30, 2017 and December 31, 2016, respectively	10,277,000	10,016,000
Capital in excess of par value	527,624,000	502,500,000
Accumulated other comprehensive income (Note 13)	20,000	0
Retained earnings	706,542,000	681,554,000
Total shareholders' equity	1,244,463,000	1,194,070,000
Total liabilities and shareholders' equity	$ 2,523,310,000	$ 2,479,303,000