EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
EARNINGS PER SHARE
Net income	$ 8,320	$ 6,322	$ 22,108	$ 18,306
Weighted average shares outstanding	20,860,000	20,793,000	20,859,000	20,795,000
Effect of dilutive securities (in shares)	81,000	95,000	80,000	96,000
Average shares outstanding including dilutive securities	20,941,000	20,888,000	20,939,000	20,891,000
Diluted earnings per share:
Antidilutive stock options (in shares)	330,150	15,500	332,150	15,500
Average antidilutive stock options (in shares)	237,118	15,500	126,684	15,500
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	$ 0.40	$ 0.31	$ 1.07	$ 0.88
Diluted earnings per share:
Diluted earnings per share	0.40	0.30	1.07	0.88
Class B Common Stock
Basic earnings per share:
Basic earnings per share	0.37	0.29	0.97	0.85
Diluted earnings per share:
Diluted earnings per share	$ 0.36	$ 0.29	$ 0.97	$ 0.85