Share Capital and Capital In Excess of Par Value (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 782,882
Balance at the beginning of the period (in shares)	99
Purchase and retirement of common shares and other	$ (1,604)	$ (1,152)
Purchase and retirement of common shares and other (in shares)	(37)	(33)
Balance at the end of the period	$ 791,395	$ 769,506
Balance at the end of the period (in shares)	102	99
Stock dividends (as a percent)	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)
Balance at the beginning of the period (in shares)	99	96
Issuance of 3% stock dividend (in shares)	3	3
Balance at the end of the period	$ (1,992)	$ (1,992)
Balance at the end of the period (in shares)	102	99
Capital in Excess of Par Value
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 719,606	$ 709,880
Issuance of 3% stock dividend	50,648	41,068
Purchase and retirement of common shares and other	(1,578)	(1,129)
Balance at the end of the period	768,676	749,819
Class B Common Stock | Common Stock.
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 19,866	$ 19,300
Balance at the beginning of the period (in shares)	28,607	27,793
Issuance of 3% stock dividend	$ 596	$ 579
Issuance of 3% stock dividend (in shares)	858	833
Conversion of Class B common shares to common shares	$ (2)
Conversion of Class B common shares to common shares (in shares)	(2)
Balance at the end of the period	$ 20,460	$ 19,879
Balance at the end of the period (in shares)	29,463	28,626
Common Stock | Common Stock.
Changes in share capital and capital in excess of par value
Balance at the beginning of the period	$ 27,584	$ 27,322
Balance at the beginning of the period (in shares)	39,721	39,344
Issuance of 3% stock dividend	$ 823	$ 817
Issuance of 3% stock dividend (in shares)	1,185	1,176
Conversion of Class B common shares to common shares	$ 2
Conversion of Class B common shares to common shares (in shares)	2
Purchase and retirement of common shares and other	$ (26)	$ (23)
Purchase and retirement of common shares and other (in shares)	(37)	(33)
Balance at the end of the period	$ 28,383	$ 28,116
Balance at the end of the period (in shares)	40,871	40,487