SHARE CAPITAL AND CAPITAL IN EXCESS OF PAR VALUE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 768,797
Balance at the beginning of the period (in shares)	96
Balance at the end of the period	$ 782,882	$ 768,797
Balance at the end of the period (in shares)	99	96
Total Number of Shares Purchased	818	921	982
Average Price Paid Per Share (in dollars per share)	$ 38.98	$ 32.76	$ 32.59
Stock dividends (as a percent)	3.00%	3.00%	3.00%
Common Stock.
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 27,322	$ 27,134	$ 26,969
Balance at the beginning of the period (in shares)	39,344	39,073	38,836
Issuance of 3% stock dividend	$ 817	$ 807	$ 804
Issuance of 3% stock dividend (in shares)	1,176	1,163	1,157
Conversion of Class B common shares to common shares	$ 13	$ 20	$ 43
Conversion of Class B common shares to common shares (in shares)	19	29	62
Purchase and retirement of common shares	$ (568)	$ (639)	$ (682)
Purchase and retirement of common shares (in shares)	(818)	(921)	(982)
Balance at the end of the period	$ 27,584	$ 27,322	$ 27,134
Balance at the end of the period (in shares)	39,721	39,344	39,073
Treasury Stock
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ (1,992)	$ (1,992)	$ (1,992)
Balance at the beginning of the period (in shares)	96	93	90
Issuance of 3% stock dividend (in shares)	3	3	3
Balance at the end of the period	$ (1,992)	$ (1,992)	$ (1,992)
Balance at the end of the period (in shares)	99	96	93
Capital in Excess of Par Value
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 709,880	$ 706,930	$ 696,059
Issuance of 3% stock dividend	41,068	32,495	42,244
Purchase and retirement of common shares	(31,342)	(29,545)	(31,373)
Balance at the end of the period	719,606	709,880	706,930
Class B Common Stock | Common Stock.
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 19,300	$ 18,758	$ 18,254
Balance at the beginning of the period (in shares)	27,793	27,012	26,287
Issuance of 3% stock dividend	$ 579	$ 562	$ 547
Issuance of 3% stock dividend (in shares)	833	810	787
Conversion of Class B common shares to common shares	$ (13)	$ (20)	$ (43)
Conversion of Class B common shares to common shares (in shares)	(19)	(29)	(62)
Balance at the end of the period	$ 19,866	$ 19,300	$ 18,758
Balance at the end of the period (in shares)	28,607	27,793	27,012