EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
EARNINGS PER SHARE
Net income	$ 19,483	$ 20,009	$ 71,310	$ 69,984
Dividends declared on Common Stock:
Undistributed net income for basic earnings per share	12,819	13,846	51,177	51,174
Weighted average potential dividends on Class A shares upon exercise of dilutive options	(21)	(17)	(70)	(40)
Undistributed net income for diluted earnings per share	$ 12,798	$ 13,829	$ 51,107	$ 51,134
Weighted average shares outstanding:
Effect of dilutive securities on Class A Shares outstanding	62,000	83,000	68,000	72,000
Weighted average shares outstanding including dilutive securities	19,981,000	20,591,000	20,134,000	20,879,000
Stock option
Diluted earnings per share:
Antidilutive stock options (in shares)	180,000	141,000	180,000	144,000
Stock option | Weighted Average
Diluted earnings per share:
Antidilutive stock options (in shares)	177,000	141,000	174,000	144,000
Class A Common Stock
EARNINGS PER SHARE
Cash dividend premium per share (as a percent)			10.00%
Dividends declared on Common Stock:
Dividends declared on Common Stock	$ (5,995)	$ (5,557)	$ (18,123)	$ (16,980)
Weighted average shares outstanding:
Weighted average shares outstanding	17,759,000	18,342,000	17,904,000	18,625,000
Basic earnings per share:
Per share dividends distributed	$ 0.34	$ 0.31	$ 1.02	$ 0.92
Undistributed earnings per share	0.65	0.68	2.58	2.48
Total basic earnings per share	0.99	0.99	3.60	3.40
Diluted earnings per share:
Per share dividends distributed	0.34	0.31	1.02	0.92
Undistributed earnings per share	0.65	0.68	2.56	2.47
Total diluted earnings per share	$ 0.99	$ 0.99	$ 3.58	$ 3.39
Class B Common Stock
Dividends declared on Common Stock:
Dividends declared on Common Stock	$ (669)	$ (606)	$ (2,010)	$ (1,830)
Weighted average shares outstanding:
Weighted average shares outstanding	2,160,000	2,166,000	2,162,000	2,182,000
Basic earnings per share:
Per share dividends distributed	$ 0.31	$ 0.28	$ 0.93	$ 0.84
Undistributed earnings per share	0.59	0.62	2.34	2.26
Total basic earnings per share	0.90	0.90	3.27	3.10
Diluted earnings per share:
Per share dividends distributed	0.31	0.28	0.93	0.84
Undistributed earnings per share	0.59	0.62	2.33	2.25
Total diluted earnings per share	$ 0.90	$ 0.90	$ 3.26	$ 3.09