CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Noncontrolling Interest	Total
Balance at Dec. 31, 2018	$ 1,011	$ 1,256,267	$ (3)	$ (1,103,692)	$ 5,469	$ 159,052
Balance (in shares) at Dec. 31, 2018	101,098
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding	$ 1	253	0	0	0	254
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding (in shares)	85
Stock-based compensation	$ 0	605	0	0	0	605
Net income	0	0	0	33,790	6,229	40,019
Other comprehensive income	0	0	13	0	0	13
Balance at Mar. 31, 2019	$ 1,012	1,257,125	10	(1,069,902)	11,698	199,943
Balance (in shares) at Mar. 31, 2019	101,183
Balance at Dec. 31, 2018	$ 1,011	1,256,267	(3)	(1,103,692)	5,469	159,052
Balance (in shares) at Dec. 31, 2018	101,098
Increase (Decrease) in Stockholders' Equity
Net income						133,131
Balance at Sep. 30, 2019	$ 1,013	1,258,370	25	(992,353)	16,708	283,763
Balance (in shares) at Sep. 30, 2019	101,279
Balance at Mar. 31, 2019	$ 1,012	1,257,125	10	(1,069,902)	11,698	199,943
Balance (in shares) at Mar. 31, 2019	101,183
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding	$ 1	200	0	0	0	201
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding (in shares)	89
Stock-based compensation	$ 0	474	0	0	0	474
Net income	0	0	0	37,740	8,321	46,061
Other comprehensive income	0	0	23	0	0	23
Balance at Jun. 30, 2019	$ 1,013	1,257,799	33	(1,032,162)	20,019	246,702
Balance (in shares) at Jun. 30, 2019	101,272
Increase (Decrease) in Stockholders' Equity
Distributions to noncontrolling interest	$ 0	0	0	0	(10,553)	(10,553)
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding	$ 0	82	0	0	0	82
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding (in shares)	7
Stock-based compensation	$ 0	489	0	0	0	489
Net income	0	0	0	39,809	7,242	47,051
Other comprehensive income	0	0	(8)	0	0	(8)
Balance at Sep. 30, 2019	$ 1,013	1,258,370	25	(992,353)	16,708	283,763
Balance (in shares) at Sep. 30, 2019	101,279
Balance at Dec. 31, 2019	$ 1,013	1,258,859	27	(946,404)	28,621	$ 342,116	[1]
Balance (in shares) at Dec. 31, 2019	101,288					101,288
Increase (Decrease) in Stockholders' Equity
Distributions to noncontrolling interest	$ 0	0	0	0	(15,810)	$ (15,810)
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding	$ 0	170	0	0	0	170
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding (in shares)	32
Stock-based compensation	$ 0	435	0	0	0	435
Net income	0	0	0	65,437	13,515	78,952
Other comprehensive income	0	0	6	0	0	6
Balance at Mar. 31, 2020	$ 1,013	1,259,464	33	(880,967)	26,326	405,869
Balance (in shares) at Mar. 31, 2020	101,320
Balance at Dec. 31, 2019	$ 1,013	1,258,859	27	(946,404)	28,621	$ 342,116	[1]
Balance (in shares) at Dec. 31, 2019	101,288					101,288
Increase (Decrease) in Stockholders' Equity
Net income						$ 218,798
Balance at Sep. 30, 2020	$ 1,014	1,260,447	0	(775,905)	49,316	$ 534,872
Balance (in shares) at Sep. 30, 2020	101,391					101,391
Balance at Mar. 31, 2020	$ 1,013	1,259,464	33	(880,967)	26,326	$ 405,869
Balance (in shares) at Mar. 31, 2020	101,320
Increase (Decrease) in Stockholders' Equity
Equity activity of noncontrolling interest from a consolidated variable interest entity	$ 0	0	0	0	350	350
Distributions to noncontrolling interest	0	0	0	0	(12,152)	(12,152)
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding	$ 2	178	0	0	0	180
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding (in shares)	72
Stock-based compensation	$ 0	375	0	0	0	375
Net income	0	0	0	76,844	21,381	98,225
Other comprehensive income	0	0	(35)	0	0	(35)
Balance at Jun. 30, 2020	$ 1,015	1,260,017	(2)	(804,123)	35,905	492,812
Balance (in shares) at Jun. 30, 2020	101,392
Increase (Decrease) in Stockholders' Equity
Equity activity of noncontrolling interest from a consolidated variable interest entity	$ 0	0	0	0	8	8
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding	$ (1)	(11)	0	0	0	(12)
Exercise of stock options, and issuance of common stock units and stock awards, net of repurchase of shares to satisfy tax withholding (in shares)	(1)
Stock-based compensation	$ 0	441	0	0	0	441
Net income	0	0	0	28,218	13,403	41,621
Other comprehensive income	0	0	2	0	0	2
Balance at Sep. 30, 2020	$ 1,014	$ 1,260,447	$ 0	$ (775,905)	$ 49,316	$ 534,872
Balance (in shares) at Sep. 30, 2020	101,391					101,391

[1] Consolidated balance sheet as of December 31, 2019 has been derived from audited consolidated financial statements.