Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Class A Common Stock	Class B Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Balance at the beginning of the period at Dec. 31, 2018	$ 2.8	$ 0.6	$ 568.3	$ 440.7	$ (121.1)	$ 891.3
Balance (in shares) at Dec. 31, 2018	27,646,465	6,329,290
Increase (Decrease) in Stockholders' Equity
Net income				99.7		99.7
Other comprehensive income (loss)					(21.1)	(21.1)
Comprehensive income						78.6
Shares of Class B common stock converted to Class A common stock (in shares)	50,000	(50,000)
Shares of Class A common stock issued upon the exercise of stock options			1.0			1.0
Shares of Class A common stock issued upon the exercise of stock options (in shares)	19,155
Stock-based compensation			13.3			13.3
Stock repurchase				(14.8)		(14.8)
Stock repurchase (in shares)	(178,340)
Net change in restricted stock units			3.3	(7.1)		(3.8)
Net change in restricted and performance stock units (in shares)	79,765
Common stock dividends				(23.6)		(23.6)
Balance at the end of the period at Sep. 29, 2019	$ 2.8	$ 0.6	585.9	494.9	(142.2)	942.0
Balance (in shares) at Sep. 29, 2019	27,617,045	6,279,290
Balance at the beginning of the period at Jun. 30, 2019	$ 2.8	$ 0.6	581.1	475.6	(125.9)	934.2
Balance (in shares) at Jun. 30, 2019	27,657,544	6,279,290
Increase (Decrease) in Stockholders' Equity
Net income				32.3		32.3
Other comprehensive income (loss)					(16.3)	(16.3)
Comprehensive income						16.0
Shares of Class A common stock issued upon the exercise of stock options			0.2			0.2
Shares of Class A common stock issued upon the exercise of stock options (in shares)	3,368
Stock-based compensation			4.6			4.6
Stock repurchase				(4.5)		(4.5)
Stock repurchase (in shares)	(47,943)
Net change in restricted stock units				(0.1)		(0.1)
Net change in restricted and performance stock units (in shares)	4,076
Common stock dividends				(8.4)		(8.4)
Balance at the end of the period at Sep. 29, 2019	$ 2.8	$ 0.6	585.9	494.9	(142.2)	942.0
Balance (in shares) at Sep. 29, 2019	27,617,045	6,279,290
Increase (Decrease) in Stockholders' Equity
Change in accounting principle						513.9
Balance at the beginning of the period at Dec. 31, 2019	$ 2.8	$ 0.6	591.5	513.9	(130.8)	978.0
Balance (in shares) at Dec. 31, 2019	27,586,416	6,279,290
Increase (Decrease) in Stockholders' Equity
Net income				85.1		85.1
Other comprehensive income (loss)					6.7	6.7
Comprehensive income						91.8
Shares of Class B common stock converted to Class A common stock (in shares)	70,000	(70,000)
Shares of Class A common stock issued upon the exercise of stock options (in shares)	661
Stock-based compensation			8.8			8.8
Stock repurchase				(24.8)		(24.8)
Stock repurchase (in shares)	(294,677)
Net change in restricted stock units			1.8	(7.8)		(6.0)
Net change in restricted and performance stock units (in shares)	83,080
Common stock dividends				(23.2)		(23.2)
Balance at the end of the period at Sep. 27, 2020	$ 2.8	$ 0.6	602.1	543.2	(124.1)	1,024.6
Balance (in shares) at Sep. 27, 2020	27,445,480	6,209,290
Balance at the beginning of the period at Jun. 28, 2020	$ 2.8	$ 0.6	598.9	521.4	(138.5)	985.2
Balance (in shares) at Jun. 28, 2020	27,461,833	6,229,290
Increase (Decrease) in Stockholders' Equity
Net income				32.9		32.9
Other comprehensive income (loss)					14.4	14.4
Comprehensive income						47.3
Shares of Class B common stock converted to Class A common stock (in shares)	20,000	(20,000)
Shares of Class A common stock issued upon the exercise of stock options (in shares)	661
Stock-based compensation			3.2			3.2
Stock repurchase				(3.7)		(3.7)
Stock repurchase (in shares)	(41,142)
Net change in restricted and performance stock units (in shares)	4,128
Common stock dividends				(7.4)		(7.4)
Balance at the end of the period at Sep. 27, 2020	$ 2.8	$ 0.6	$ 602.1	$ 543.2	$ (124.1)	1,024.6
Balance (in shares) at Sep. 27, 2020	27,445,480	6,209,290
Increase (Decrease) in Stockholders' Equity
Change in accounting principle						$ 543.2