Share Capital and Capital In Excess of Par Value (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Changes in share capital and capital in excess of par value
Balance at the beginning of the period			$ 823,107
Balance at the beginning of the period (in shares)			102
Purchase and retirement of common shares and other				$ (16,548)
Purchase and retirement of common shares and other (in shares)			0	(429)
Balance at the end of the period	$ 841,094	$ 785,074	$ 841,094	$ 785,074
Balance at the end of the period (in shares)	105	102	105	102
Stock dividends (as a percent)	3.00%	3.00%	3.00%	3.00%
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)	$ (1,992)
Balance at the beginning of the period (in shares)	105	102	102	99
Issuance of 3% stock dividend (in shares)			3	3
Balance at the end of the period	$ (1,992)	$ (1,992)	$ (1,992)	$ (1,992)
Balance at the end of the period (in shares)	105	102	105	102
Capital in Excess of Par Value
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 802,253	$ 768,676	$ 737,453	$ 719,606
Issuance of 3% stock dividend			64,800	50,648
Purchase and retirement of common shares and other		(14,837)		(16,415)
Balance at the end of the period	802,253	753,839	802,253	753,839
Class B Common Stock | Common Stock
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 21,049	$ 20,460	$ 20,448	$ 19,866
Balance at the beginning of the period (in shares)	30,311	29,463	29,445	28,607
Issuance of 3% stock dividend			$ 613	$ 596
Issuance of 3% stock dividend (in shares)			882	858
Conversion of Class B common shares to common shares	$ (1)	$ (7)	$ (13)	$ (9)
Conversion of Class B common shares to common shares (in shares)	(2)	(11)	(18)	(13)
Balance at the end of the period	$ 21,048	$ 20,453	$ 21,048	$ 20,453
Balance at the end of the period (in shares)	30,309	29,452	30,309	29,452
Common Stock | Common Stock
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 28,619	$ 28,383	$ 27,777	$ 27,584
Balance at the beginning of the period (in shares)	41,211	40,871	39,999	39,721
Issuance of 3% stock dividend			$ 830	$ 823
Issuance of 3% stock dividend (in shares)			1,196	1,185
Conversion of Class B common shares to common shares	$ 1	$ 7	$ 13	$ 9
Conversion of Class B common shares to common shares (in shares)	2	11	18	13
Purchase and retirement of common shares and other		$ (272)		$ (298)
Purchase and retirement of common shares and other (in shares)		(392)		(429)
Balance at the end of the period	$ 28,620	$ 28,118	$ 28,620	$ 28,118
Balance at the end of the period (in shares)	41,213	40,490	41,213	40,490