EARNINGS PER SHARE AND DIVIDEND DATA (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Income (Numerator) [Abstract]
Income available to common shareholders	$ 132,728	$ 127,491	$ 116,750
Income available to common shareholders plus assumed exercise	$ 132,728	$ 127,491	$ 116,750
Shares (Denominator) [Abstract]
Income available to common shareholders (in shares)	94,219,000	95,825,000	95,973,000
Effect of dilutive stock options (in shares)	236,000	299,000	329,000
Income available to common shareholders plus assumed exercise (in shares)	94,455,000	96,124,000	96,302,000
Per share amount [Abstract]
Income available to common shareholders (in dollars per share)	$ 1.41	$ 1.33	$ 1.22
Income available to common shareholders plus assumed exercise all outstanding share-based awards (in dollars per share)	$ 1.41	$ 1.33	$ 1.21
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted shares (in shares)	9,450	32,000	67,000
Weighted average exercise price of antidilutive securities (in dollars per share)	$ 25.31	$ 25.31	$ 24.89
Other Equity Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted shares (in shares)				0