Consolidated Statement of Equity (Statement) - USD ($) $ in Thousands	Total	Parent [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Shares, Issued			65,955,080			(55,927)
Issuance of stock awards, net of forfeitures			177,945
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Purchase of treasury shares						(87,063)
Issuance of treasury shares			0			78,395
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	$ (4,494)	(4,494)				(4,494)
Issuance of stock awards, net of forfeitures		0	2	(2)
Share-based Compensation expense	10,779	10,779		10,779
Issuance of treasury shares		0	0	(4,288)		4,288
Non-employee directors' deferred compensation plan		(142)		0		(142)
Net income (loss)	$ (173,396)	(173,396)			(173,396)
Stockholders' Equity, Other		(90)		(90)
Stockholders' Equity Ending, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2018		$ 2,340,306	$ 661	$ 2,509,693	$ (166,692)	$ (3,356)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Shares, Issued			66,133,025			(67,169)