Per Share Amounts and Common Shares Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Oct. 01, 2022	Sep. 30, 2023	Oct. 01, 2022
Equity [Abstract]
Net income	$ 20,697	$ 20,464	$ 58,736	$ 49,031
Weighted-average shares outstanding, basic	42,809,000	43,920,000	42,452,000	44,194,000
Weighted-average shares, partially-paid share subscriptions	314,000	228,000	942,000	228,000
Basic weighted average shares	43,123,000	44,148,000	43,394,000	44,422,000
Incremental shares from assumed exercise of stock subscription purchase rights	38,000	0	38,000	0
Incremental shares from assumed exercise of stock options and awards	2,025,000	2,257,000	2,068,000	2,297,000
Diluted weighted-average shares	45,186,000	46,405,000	45,501,000	46,719,000
Net income per share basic	$ 0.48	$ 0.46	$ 1.35	$ 1.10
Net income per share diluted	$ 0.46	$ 0.44	$ 1.29	$ 1.05
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at January 1, 2023			42,717,484
Shares purchased			(2,615,619)
Shares sold			1,303,950
Stock subscription offering -- cash purchases			12,336
Options and awards exercised			513,305
Shares outstanding at September 30, 2023	41,931,456		41,931,456
Employee options exercisable	1,545,520		1,545,520
Common stock, shares subscribed but unissued	1,256,250		1,256,250
Purchase rights, outstanding	462,473		462,473
Common shares, net of treasury shares [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at January 1, 2023			33,529,474
Shares purchased			(1,641,224)
Shares sold			789,553
Stock subscription offering -- cash purchases			12,336
Options and awards exercised			513,305
Shares outstanding at September 30, 2023	33,203,444		33,203,444
Redeemable shares [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at January 1, 2023			9,188,010
Shares purchased			(974,395)
Shares sold			514,397
Stock subscription offering -- cash purchases			0
Options and awards exercised			0
Shares outstanding at September 30, 2023	8,728,012		8,728,012
Stock option plans [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee options exercisable	1,545,520		1,545,520