EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
EARNINGS PER SHARE
Net income	$ 5,640	$ 5,246	$ 27,748	$ 23,552
Weighted average shares outstanding	20,848,000	20,797,000	20,856,000	20,795,000
Effect of dilutive securities (in shares)	86,000	94,000	80,000	96,000
Average shares outstanding including dilutive securities	20,934,000	20,891,000	20,936,000	20,891,000
Diluted earnings per share:
Antidilutive stock options (in shares)	23,000	16,000	323,100	16,000
Average antidilutive stock options (in shares)	20,300	16,000	186,969	15,000
Class A Common Stock
EARNINGS PER SHARE
Cash dividend premium per share (as a percent)			10.00%
Basic earnings per share:
Basic earnings per share	$ 0.27	$ 0.25	$ 1.34	$ 1.14
Diluted earnings per share:
Diluted earnings per share	0.27	0.25	1.34	1.13
Class B Common Stock
Basic earnings per share:
Basic earnings per share	0.25	0.24	1.22	1.09
Diluted earnings per share:
Diluted earnings per share	$ 0.25	$ 0.24	$ 1.22	$ 1.08