CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ (321,421)	$ 5,910	$ (318,634)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion, amortization and impairment	916,318	783,341	668,434
Impairment of goodwill	211,129
Dry holes and abandonments	915	1,929	58
Deferred income tax benefit	(41,185)	(330,346)	(152,160)
Stock-based compensation expense	37,925	44,483	28,324
Net gain on asset disposals	(28,958)	(33,510)	(14,771)
Tax expense related to stock-based compensation			(4,868)
Amortization of debt discount and issuance costs	830	346	2,270
Changes in operating assets and liabilities:
Accounts receivable	23,515	(239,482)	72,327
Income taxes receivable/payable	(1,555)	990	30,379
Inventory and other assets	(1,470)	(23,449)	5,664
Accounts payable	(69,453)	104,072	12,024
Accrued expenses	4,136	(14,190)	(24,573)
Other liabilities	(56)	617	560
Net cash provided by operating activities	730,670	300,711	305,034
Cash flows from investing activities:
Acquisitions, net of cash acquired	(14,211)	(501,954)	155
Purchases of property and equipment	(641,458)	(567,087)	(119,799)
Proceeds from disposal of assets	47,357	60,945	21,889
Collection of note receivable	23,760
Other investments		(2,520)
Net cash used in investing activities	(584,552)	(1,010,616)	(97,755)
Cash flows from financing activities:
Proceeds from equity offering		471,570
Purchases of treasury stock	(161,737)	(6,809)	(3,610)
Dividends paid	(30,589)	(16,315)	(23,579)
Proceeds from long-term debt	521,194
Repayment of long-term debt			(255,000)
Proceeds from borrowings under revolving credit facility	79,000	599,000	200,500
Repayment of borrowings under revolving credit facility	(347,000)	(331,000)	(200,500)
Debt issuance costs	(4,489)		(3,357)
Proceeds from exercise of stock options	485	123	268
Net cash provided by (used in) financing activities	56,864	716,569	(285,278)
Effect of foreign exchange rate changes on cash	(781)	1,012	(195)
Net increase (decrease) in cash and cash equivalents	202,201	7,676	(78,194)
Cash and cash equivalents at beginning of year	42,828	35,152	113,346
Cash and cash equivalents at end of year	245,029	42,828	35,152
Net cash (paid) received during the year for:
Interest, net of capitalized interest of $1,435 in 2018, $1,175 in 2017 and $398 in 2016	(41,184)	(34,953)	(36,551)
Income taxes	3,172	3,947	52,716
Non-cash investing and financing activities:
Receivable from property and equipment insurance	15,000
Net increase in payables for purchases of property and equipment	36,241	17,228	28,926
Issuance of common stock for business acquisitions	2,932	1,226,890	6,733
Net decrease (increase) in deposits on equipment purchases	$ 4,311	$ (301)	$ 6,317