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						86,080
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
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
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						$ 177,177
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					101,392
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
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)
Equity activity of noncontrolling interest from a consolidated variable interest entity	0	0	0	0	350	350
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					101,392
Increase (Decrease) in Stockholders' Equity
Contributions from noncontrolling interest	$ 0	$ 0	$ 0	$ 0	$ 350	$ 350

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