THREE-FOR-TWO STOCK SPLIT - Effects of Stock Split on Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
STOCKHOLDERS’ EQUITY
Preferred stock, without par value; 500,000 authorized, zero shares issued			$ 0	$ 0
Common stock, par value $1 per share; 250,000,000 shares authorized, 218,482,907 shares issued	218,483		217,992	217,792
Treasury Stock, par value $1 per share ; 200,000 and 0 shares, respectively	(200)
Paid-in-capital	62,839		81,405	77,452
Accumulated other comprehensive loss	(65,488)		(45,956)	(70,075)
Retained earnings	247,042		400,483	343,376
Total Stockholders’ Equity	$ 462,676		$ 653,924	$ 568,545	$ 524,029
Shares issued during the period (in shares)	72,760,969	72,932,222
Preferred stock, authorized (in shares)			500,000	500,000	500,000
Preferred stock, issued (in shares)			0	0	0
Common stock, par value (in dollars per share)			$ 1	$ 1	$ 1
Common stock, authorized (in shares)			375,000,000	375,000,000	250,000,000
Common stock, issued (in shares)			217,992,177	217,791,511	218,482,907
Treasury stock (in shares)					200,000
Pro forma
STOCKHOLDERS’ EQUITY
Preferred stock, without par value; 500,000 authorized, zero shares issued
Common stock, par value $1 per share; 250,000,000 shares authorized, 218,482,907 shares issued	145,722
Treasury Stock, par value $1 per share ; 200,000 and 0 shares, respectively	(200)
Paid-in-capital	62,839
Accumulated other comprehensive loss	(65,488)
Retained earnings	319,803
Total Stockholders’ Equity	462,676
Adjustment
STOCKHOLDERS’ EQUITY
Common stock, par value $1 per share; 250,000,000 shares authorized, 218,482,907 shares issued	72,761
Retained earnings	$ (72,761)