EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
EARNINGS PER SHARE
Net income	$ 9,828	$ 5,640	$ 35,903	$ 27,748
Weighted average shares outstanding	20,925,000	20,848,000	20,946,000	20,856,000
Effect of dilutive securities (in shares)	13,000	86,000	11,000	80,000
Average shares outstanding including dilutive securities	20,938,000	20,934,000	20,957,000	20,936,000
Diluted earnings per share:
Antidilutive stock options (in shares)	5,000	23,000	7,500	323,100
Average antidilutive stock options (in shares)	2,500	20,300	5,000	186,969
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	$ 0.47	$ 0.27	$ 1.73	$ 1.34
Diluted earnings per share:
Diluted earnings per share	0.47	0.27	1.73	1.34
Class B Common Stock
Basic earnings per share:
Basic earnings per share	0.43	0.25	1.58	1.22
Diluted earnings per share:
Diluted earnings per share	$ 0.43	$ 0.25	$ 1.57	$ 1.22