SUMMARY OF QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated quarterly financial data
Interest income	$ 51,379	$ 53,772	$ 51,552	$ 69,557	$ 57,970	$ 56,038	$ 57,091	$ 81,159	$ 226,260	$ 252,258	$ 280,883
Interest expense	1,038	1,340	1,511	1,777	2,850	3,786	4,886	8,421	5,666	19,943	44,757
NET INTEREST INCOME	50,341	52,432	50,041	67,780	55,120	52,252	52,205	72,738	220,594	232,315	236,126
Provision for loan and lease losses.	2,577	1,292	(4,323)	15,262	484	1,500	6,534	22,760	14,808	31,278	25,758
NET INTEREST INCOME AFTER PROVISION	47,764	51,140	54,364	52,518	54,636	50,752	45,671	49,978	205,786	201,037	210,368
Noninterest income (3)	16,630	19,339	21,853	29,037	17,136	20,597	18,751	30,569	86,859	87,053	75,008
Noninterest expense (4)	44,585	44,252	45,656	47,811	48,140	45,523	44,825	46,969	182,304	185,457	172,183
INCOME BEFORE INCOME TAX EXPENSE	19,809	26,227	30,561	33,744	23,632	25,826	19,597	33,578	110,341	102,633	113,193
Income tax expense	3,004	6,218	6,639	7,691	3,276	5,437	3,793	6,881	23,552	19,387	21,494
NET INCOME	$ 16,805	$ 20,009	$ 23,922	$ 26,053	$ 20,356	$ 20,389	$ 15,804	$ 26,697	$ 86,789	$ 83,246	$ 91,699
Class A Common Stock
Basic earnings per share:
Basic earnings per share (in dollars per share)	$ 0.84	$ 0.99	$ 1.16	$ 1.26	$ 0.98	$ 0.98	$ 0.77	$ 1.29	$ 4.25	$ 4.00	$ 4.41
Diluted earnings per share:
Diluted earnings per share (in dollars per share)	0.84	0.99	1.16	1.25	0.98	0.98	0.76	1.28	4.24	3.99	4.39
Dividends declared per common share:
Dividend declared common stock, per share (in dollars per share)	0.308	0.308	0.308	0.308	0.286	0.286	0.286	0.286	1.232	1.144	1.056
Class B Common Stock
Basic earnings per share:
Basic earnings per share (in dollars per share)	0.77	0.90	1.05	1.14	0.89	0.89	0.69	1.17	3.87	3.64	4.01
Diluted earnings per share:
Diluted earnings per share (in dollars per share)	0.76	0.90	1.05	1.14	0.89	0.89	0.69	1.16	3.85	3.63	3.99
Dividends declared per common share:
Dividend declared common stock, per share (in dollars per share)	$ 0.280	$ 0.280	$ 0.280	$ 0.280	$ 0.260	$ 0.260	$ 0.260	$ 0.260	$ 1.12	$ 1.04	$ 0.96