CONSOLIDATED STATEMENTS OF EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock Par Value [Member]	Capital in Excess of Par Value [Member]	Retained Earnings/(Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) ("AOCI") [Member]	Treasury Stock [Member]	Stockholder's Equity [Member]	Noncontrolling Interest ("NCI") [Member]
Beginning Balance at Dec. 31, 2016					$ (66,895)
Net income	$ 24,195
Other comprehensive loss, net of tax					2,411
Ending Balance at Mar. 31, 2017					(64,484)
Beginning Balance at Dec. 31, 2017	1,788,777	$ 292,526	$ 1,663,091	$ (48,221)	(50,448)	$ (96,282)	$ 1,760,666	$ 28,111
Adoption of ASC 606 at Dec. 31, 2017	19,944			19,944			19,944
Balance at January 1, 2018 at Dec. 31, 2017	1,808,721	292,526	1,663,091	(28,277)	(50,448)	(96,282)	1,780,610	28,111
Net income	34,122			35,189			35,189	(1,067)
Other comprehensive loss, net of tax	(359)				(359)		(359)
Common stock issued		2,740	(2,740)
Stock-based compensation charges	2,982		2,982				2,982
Purchase of treasury shares	(6,513)					(6,513)	(6,513)
Retirement of common stock		(859)	(5,589)			6,448
Ending Balance at Mar. 31, 2018	$ 1,838,953	$ 294,407	$ 1,657,744	$ 6,912	$ (50,807)	$ (96,347)	$ 1,811,909	$ 27,044