EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
EARNINGS PER SHARE
Net income	$ 23,901	$ 23,922	$ 51,827	$ 49,975
Dividends declared on Common Stock:
Undistributed net income for basic earnings per share	17,184	17,634	38,358	37,328
Weighted average potential dividends on Class A shares upon exercise of dilutive options	(21)	(17)	(49)	(40)
Undistributed net income for diluted earnings per share	$ 17,163	$ 17,617	$ 38,309	$ 37,288
Weighted average shares outstanding:
Effect of dilutive securities on Class A Shares outstanding	62,000	55,000	71,000	65,000
Weighted average shares outstanding including dilutive securities	20,169,000	20,949,000	20,202,000	21,016,000
Stock option
Diluted earnings per share:
Antidilutive stock options (in shares)	187,000	149,000	186,000	169,000
Stock option | Weighted Average
Diluted earnings per share:
Antidilutive stock options (in shares)	184,000	149,000	178,000	166,000
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	$ (6,047)	$ (5,680)	$ (12,128)	$ (11,423)
Weighted average shares outstanding:
Weighted average shares outstanding	17,946,000	18,712,000	17,968,000	18,761,000
Basic earnings per share:
Per share dividends distributed	$ 0.34	$ 0.31	$ 0.68	$ 0.62
Undistributed earnings per share	0.86	0.85	1.92	1.80
Total basic earnings per share	1.20	1.16	2.60	2.42
Diluted earnings per share:
Per share dividends distributed	0.34	0.31	0.68	0.62
Undistributed earnings per share	0.86	0.85	1.91	1.79
Total diluted earnings per share	$ 1.20	$ 1.16	$ 2.59	$ 2.41
Class B Common Stock
Dividends declared on Common Stock:
Dividends declared on Common Stock	$ (670)	$ (608)	$ (1,341)	$ (1,224)
Weighted average shares outstanding:
Weighted average shares outstanding	2,161,000	2,182,000	2,163,000	2,190,000
Basic earnings per share:
Per share dividends distributed	$ 0.31	$ 0.28	$ 0.62	$ 0.56
Undistributed earnings per share	0.78	0.77	1.75	1.64
Total basic earnings per share	1.09	1.05	2.37	2.20
Diluted earnings per share:
Per share dividends distributed	0.31	0.28	0.62	0.56
Undistributed earnings per share	0.78	0.77	1.74	1.63
Total diluted earnings per share	$ 1.09	$ 1.05	$ 2.36	$ 2.19