EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Calculation of basic earnings per share:
Net income	$ 83,639	$ 78,291
Average shares issued and outstanding	78,627,003	78,206,920
Issuable under various deferred compensation plans (in shares)	981,458	932,472
Weighted shares outstanding - basic	79,608,461	79,139,392
Per share:
Net income - basic (in dollars per share)	$ 1.05	$ 0.99
Calculation of diluted earnings per share:
Net income	$ 83,639	$ 78,291
Weighted shares outstanding - basic	79,608,461	79,139,392
Stock appreciation rights ("SARs") (in shares)	466,251	440,164
Issuable under various other stock-based compensation plans (in shares)	565,664	812,749
Restricted stock units (in shares)	231,776	314,439
Weighted shares outstanding - diluted	80,872,152	80,706,744
Per share:
Net income - diluted (in dollars per share)	$ 1.03	$ 0.97
Antidilutive securities (in shares)		670,320