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, 2017	$ 2.8	$ 0.6	$ 551.8	$ 372.9	$ (99.1)	$ 829.0
Balance (in shares) at Dec. 31, 2017	27,724,192	6,379,290
Increase (Decrease) in Stockholders' Equity
Change in accounting principle				(0.7)		(0.7)
Net income				95.7		95.7
Other comprehensive income (loss)					(10.7)	(10.7)
Comprehensive income						85.0
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			2.1			2.1
Shares of Class A common stock issued upon the exercise of stock options (in shares)	37,632
Stock-based compensation			10.0			10.0
Stock repurchase				(15.5)		(15.5)
Stock repurchase (in shares)	(195,790)
Issuance of net shares of restricted Class A common stock				(3.1)		(3.1)
Issuance of net shares of restricted Class A common stock (in shares)	114,461
Net change in restricted stock and performance stock units			0.6	(2.1)		(1.5)
Net change in restricted and performance stock units (in shares)	50,932
Common stock dividends				(21.1)		(21.1)
Balance at the end of the period at Sep. 30, 2018	$ 2.8	$ 0.6	564.5	426.1	(109.8)	884.2
Balance (in shares) at Sep. 30, 2018	27,781,427	6,329,290
Balance at the beginning of the period at Jul. 01, 2018	$ 2.8	$ 0.6	559.6	407.4	(112.2)	858.2
Balance (in shares) at Jul. 01, 2018	27,803,429	6,329,290
Increase (Decrease) in Stockholders' Equity
Net income				31.5		31.5
Other comprehensive income (loss)					2.4	2.4
Comprehensive income						33.9
Shares of Class A common stock issued upon the exercise of stock options			2.1			2.1
Shares of Class A common stock issued upon the exercise of stock options (in shares)	25,049
Stock-based compensation			3.7			3.7
Stock repurchase				(4.7)		(4.7)
Stock repurchase (in shares)	(57,156)
Issuance of net shares of restricted Class A common stock				(0.9)		(0.9)
Issuance of net shares of restricted Class A common stock (in shares)	17,988
Net change in restricted stock and performance stock units			(0.9)			(0.9)
Net change in restricted and performance stock units (in shares)	(7,883)
Common stock dividends				(7.2)		(7.2)
Balance at the end of the period at Sep. 30, 2018	$ 2.8	$ 0.6	564.5	426.1	(109.8)	884.2
Balance (in shares) at Sep. 30, 2018	27,781,427	6,329,290
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 and performance 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 and performance 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