CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Common stock held in treasury	Additional Paid-in Capital	Retained (deficit)/earnings	Accumulated other comprehensive loss
Beginning balance at Dec. 31, 2017	$ 5,774,272	$ 2,481	$ (599)	$ 5,577,732	$ 195,990	$ (1,332)
Beginning balance Shares at Dec. 31, 2017		248,144,000
Issuance of common stock	(1,217)	$ 11		(1,228)
Issuance of common stock, shares		1,092,000
Stock-based compensation expense	17,201			17,201
Cash dividends paid ($0.02 per share)	(4,971)				(4,971)
Treasury stock issuance			30	(30)
Other comprehensive income	69					69
Net income (loss)	49,238				49,238
Ending balance at Mar. 31, 2018	5,834,592	$ 2,492	(569)	5,593,675	240,257	(1,263)
Ending balance Shares at Mar. 31, 2018		249,236,000
Beginning balance at Dec. 31, 2017	5,774,272	$ 2,481	(599)	5,577,732	195,990	(1,332)
Beginning balance Shares at Dec. 31, 2017		248,144,000
Net income (loss)	17,941
Ending balance at Sep. 30, 2018	5,817,288	$ 2,495	(404)	5,617,371	198,950	(1,124)
Ending balance Shares at Sep. 30, 2018		249,504,000
Beginning balance at Dec. 31, 2017	5,774,272	$ 2,481	(599)	5,577,732	195,990	(1,332)
Beginning balance Shares at Dec. 31, 2017		248,144,000
Ending balance at Dec. 31, 2018	$ 4,059,431	$ 2,495	(391)	5,628,447	(1,570,462)	(658)
Ending balance Shares at Dec. 31, 2018	249,519,687	249,520,000
Beginning balance at Mar. 31, 2018	$ 5,834,592	$ 2,492	(569)	5,593,675	240,257	(1,263)
Beginning balance Shares at Mar. 31, 2018		249,236,000
Issuance of common stock	6,545	$ 2		6,543
Issuance of common stock, shares		201,000
Stock-based compensation expense	7,654			7,654
Cash dividends paid ($0.02 per share)	(4,989)				(4,989)
Treasury stock issuance			165	(165)
Other comprehensive income	69					69
Net income (loss)	(79,836)				(79,836)
Ending balance at Jun. 30, 2018	5,764,035	$ 2,494	(404)	5,607,707	155,432	(1,194)
Ending balance Shares at Jun. 30, 2018		249,437,000
Issuance of common stock	3,439	$ 1		3,438
Issuance of common stock, shares		65,000
Issuance of common stock upon vesting of PSUs				31	(31)
Issuance of common stock upon vesting of PSUs, shares		2,000
Stock-based compensation expense	6,195			6,195
Cash dividends paid ($0.02 per share)	(4,990)				(4,990)
Other comprehensive income	70					70
Net income (loss)	48,539				48,539
Ending balance at Sep. 30, 2018	5,817,288	$ 2,495	(404)	5,617,371	198,950	(1,124)
Ending balance Shares at Sep. 30, 2018		249,504,000
Beginning balance at Dec. 31, 2018	$ 4,059,431	$ 2,495	(391)	5,628,447	(1,570,462)	(658)
Beginning balance Shares at Dec. 31, 2018	249,519,687	249,520,000
Issuance of common stock	$ (2,379)	$ 17		(2,396)
Issuance of common stock, shares		1,628,000
Issuance of common stock upon vesting of PSUs				4	(4)
Stock-based compensation expense	9,155			9,155
Cash dividends paid ($0.02 per share)	(5,023)				(5,023)
Other comprehensive income	60					60
Net income (loss)	1,419				1,419
Ending balance at Mar. 31, 2019	4,062,663	$ 2,512	(391)	5,635,210	(1,574,070)	(598)
Ending balance Shares at Mar. 31, 2019		251,148,000
Beginning balance at Dec. 31, 2018	$ 4,059,431	$ 2,495	(391)	5,628,447	(1,570,462)	(658)
Beginning balance Shares at Dec. 31, 2018	249,519,687	249,520,000
Net income (loss)	$ 89,023
Ending balance at Sep. 30, 2019	$ 4,158,192	$ 2,514	(328)	5,653,005	(1,496,521)	(478)
Ending balance Shares at Sep. 30, 2019	251,425,437	251,425,000
Beginning balance at Mar. 31, 2019	$ 4,062,663	$ 2,512	(391)	5,635,210	(1,574,070)	(598)
Beginning balance Shares at Mar. 31, 2019		251,148,000
Issuance of common stock	1,549	$ 2		1,547
Issuance of common stock, shares		206,000
Issuance of common stock upon vesting of PSUs				1	(1)
Stock-based compensation expense	7,822			7,822
Cash dividends paid ($0.02 per share)	(5,026)				(5,026)
Other comprehensive income	60					60
Net income (loss)	115,185				115,185
Ending balance at Jun. 30, 2019	4,182,253	$ 2,514	(391)	5,644,580	(1,463,912)	(538)
Ending balance Shares at Jun. 30, 2019		251,354,000
Issuance of common stock	1,170			1,170
Issuance of common stock, shares		71,000
Stock-based compensation expense	7,318			7,318
Cash dividends paid ($0.02 per share)	(5,028)				(5,028)
Treasury stock issuance			63	(63)
Other comprehensive income	60					60
Net income (loss)	(27,581)				(27,581)
Ending balance at Sep. 30, 2019	$ 4,158,192	$ 2,514	$ (328)	$ 5,653,005	$ (1,496,521)	$ (478)
Ending balance Shares at Sep. 30, 2019	251,425,437	251,425,000