Consolidated Statement of Equity (Statement) - USD ($) $ in Thousands	Total	Parent [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock, Common [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Shares, Issued			(65,955,080)				55,927
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			43,930
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Purchase of treasury shares							41,357
Issuance of treasury shares			0				70,603
Non-employee directors' deferred compensation plan							(2,574)
Stockholders' Equity Beginning, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2017		$ 2,507,649	$ 659	$ 2,503,294		$ 6,704	$ (3,008)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury shares		(2,255)					(2,255)
Share-based Compensation expense		5,261	1	5,260
Issuance of treasury shares		0	0	3,891			(3,891)
Non-employee directors' deferred compensation plan		(142)		0			(142)
Net income (loss)		(13,139)				(13,139)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Mar. 31, 2018		2,497,374	660	2,504,663		(6,435)	(1,514)
Stockholders' Equity Beginning, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2017		2,507,649	659	2,503,294		6,704	(3,008)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Compensation expense	$ 16,357
Net income (loss)	(176,830)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2018		2,342,244	$ 661	2,514,861		(170,126)	$ (3,152)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Repurchased and Retired During Period, Value	0
Shares, Issued			(65,999,010)				(29,255)
Purchase of treasury shares					45,706
Issuance of treasury shares			0				7,792
Stockholders' Equity Beginning, Including Portion Attributable to Noncontrolling Interest at Mar. 31, 2018		2,497,374	$ 660	2,504,663		(6,435)	$ (1,514)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury shares		(2,239)			$ (2,239)
Issuance of treasury shares		0	(1)	397			(397)
Net income (loss)		(160,257)				(160,257)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2018		2,340,306	$ 661	2,509,693		(166,692)	$ (3,356)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Issued for Services				5,517
Stockholders' Equity, Other		(90)		(90)
Stock Issued During Period, Shares, Issued for Services			134,015
Shares, Issued			(66,133,025)				(67,169)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value		5,518
Purchase of treasury shares					3,402
Issuance of treasury shares					8,306
Purchase of treasury shares		(206)			$ (206)
Issuance of treasury shares			$ 0	410	$ (410)
Net income (loss)	(3,434)	(3,434)				(3,434)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2018		2,342,244	$ 661	2,514,861		(170,126)	$ (3,152)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Issued for Services				5,578
Stock Issued During Period, Shares, Issued for Services			3,402
Shares, Issued			(66,136,427)				62,265
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value		5,578
Shares, Issued			(66,148,609)				(45,220)
Purchase of treasury shares					41,787
Issuance of treasury shares					64,372
Stockholders' Equity Beginning, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2018		2,526,708	$ 661	2,519,423		8,727	$ (2,103)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury shares		(1,460)			$ (1,460)
Issuance of treasury shares			(1)	(2,547)	$ (2,547)
Net income (loss)		(120,176)				(120,176)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Mar. 31, 2019		2,409,755	$ 662	2,521,558		(111,449)	(1,016)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Issued for Services				4,682
Stock Issued During Period, Shares, Issued for Services			48,254
Stockholders' Equity Beginning, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2018		2,526,708	$ 661	2,519,423		8,727	(2,103)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Compensation expense	18,124
Net income (loss)	(35,720)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2019		2,359,755	$ 621	2,390,658		(26,993)	$ (4,531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Repurchased During Period, Shares					(4,400,000)
Stock Repurchased During Period, Value	(142,665)
Stock Repurchased and Retired During Period, Value	(142,665)
Shares, Issued			(66,196,863)				(22,635)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value		4,683
Purchase of treasury shares					54,784
Issuance of treasury shares			0				24,604
Stockholders' Equity Beginning, Including Portion Attributable to Noncontrolling Interest at Mar. 31, 2019		2,409,755	$ 662	2,521,558		(111,449)	$ (1,016)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury shares		(2,257)			$ (2,257)
Issuance of treasury shares		0	(1)	995			(995)
Net income (loss)		68,548				68,548
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2019		2,378,406	$ 635	2,433,974		(42,901)	$ (13,302)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares, Retired			(2,182)				2,182
Treasury Stock, Retired, Cost Method, Amount				(78)	$ 78
Stock Repurchased During Period, Shares					(3,136,406)
Stock Repurchased and Retired During Period, Shares			(2,822,259)		2,822,259
Stock Repurchased During Period, Value		(105,215)			$ (105,215)
Stock Repurchased and Retired During Period, Value			$ (28)	(94,085)	$ 94,113
Stock Issued During Period, Value, Issued for Services				7,574
Stock Issued During Period, Shares, Issued for Services			148,040
Shares, Issued			(63,520,462)				364,780
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value		7,575
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			10,808
Purchase of treasury shares					4,750
Issuance of treasury shares			0				14,973
Purchase of treasury shares		(157)			$ (157)
Share-based Compensation expense		5,866	$ 0	5,866
Issuance of treasury shares		0	0	614			$ (614)
Net income (loss)	$ 15,908	15,908				15,908
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2019		2,359,755	$ 621	2,390,658		$ (26,993)	$ (4,531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares, Retired			(995)				995
Treasury Stock, Retired, Cost Method, Amount				(32)	$ 32
Stock Repurchased During Period, Shares					(1,228,310)
Stock Repurchased and Retired During Period, Shares			(1,442,457)		1,442,457
Stock Repurchased During Period, Value		$ (40,268)			$ (40,268)
Stock Repurchased and Retired During Period, Value			$ (14)	$ (48,536)	$ 48,550
Shares, Issued			(62,087,818)				139,415