CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Common Stock	Additional Paid In Capital.	Retained Earnings Class A Common Stock	Retained Earnings Class B Common Stock	Retained Earnings	Accumulated Other Comprehensive Income	Class A Common Stock	Class B Common Stock	Total
Increase (Decrease) in Stockholders' Equity
Adjustment for adoption							$ 126				$ 126
Balance at beginning of period at Dec. 31, 2018			$ 4,900	$ 141,018			545,013	$ (997)			689,934
Balance (in shares) at Dec. 31, 2018	18,675	2,213
Increase (Decrease) in Stockholders' Equity
Net income							29,516				29,516
Net change in accumulated other comprehensive income								2,794			2,794
Dividends declared on Common Stock:
Dividends declared on Common Stock					$ (4,933)	$ (531)			$ (4,933)	$ (531)
Repurchase of Class A Common Stock			(1)	(376)			(2)				(379)
Repurchase of Class A Common Stock (in shares)	(8)
Net change in notes receivable on Class A Common Stock				(34)							(34)
Deferred director compensation expense - Class A Common Stock				65							65
Deferred director compensation expense - Class A Common Stock (in shares)	5
Deferred designed key employee compensation expense - Class A Common Stock				168							168
Employee stock purchase plan - Class A Common Stock				121							121
Employee stock purchase plan - Class A Common Stock (in shares)	3
Stock-based awards, Performance stock units				(57)							(57)
Stock-based awards, Performance stock units (in shares)	23
Stock-based awards, Restricted stock				180							180
Stock-based awards, Stock options				121							121
Balance at end of period at Mar. 31, 2019			4,899	141,206			569,189	1,797			717,091
Balance (in shares) at Mar. 31, 2019	18,698	2,213
Increase (Decrease) in Stockholders' Equity
Adjustment for adoption							(4,291)				(4,291)
Balance at beginning of period at Dec. 31, 2019			4,907	142,068			614,171	3,098			764,244
Balance (in shares) at Dec. 31, 2019	18,737	2,206
Increase (Decrease) in Stockholders' Equity
Net income							26,697				26,697
Net change in accumulated other comprehensive income								5,733			5,733
Dividends declared on Common Stock:
Dividends declared on Common Stock					$ (5,358)	$ (572)			$ (5,358)	$ (572)
Stock options exercised, net of shares withheld			1	(43)							(42)
Stock options exercised, net of shares withheld (in shares)	2
Conversion of Class B Common Stock to Class A Common Stock (in shares)	6	(6)
Repurchase of Class A Common Stock			(20)	(582)			(2,250)				(2,852)
Repurchase of Class A Common Stock (in shares)	(86)
Net change in notes receivable on Class A Common Stock				30							30
Deferred director compensation expense - Class A Common Stock				79							79
Deferred director compensation expense - Class A Common Stock (in shares)	4
Deferred designed key employee compensation expense - Class A Common Stock				143							143
Employee stock purchase plan - Class A Common Stock			1	154							155
Employee stock purchase plan - Class A Common Stock (in shares)	5
Stock-based awards, Performance stock units				(200)							(200)
Stock-based awards, Performance stock units (in shares)	18
Stock-based awards, Restricted stock			1	187							188
Stock-based awards, Restricted stock (in shares)	1
Stock-based awards, Stock options				92							92
Balance at end of period at Mar. 31, 2020			$ 4,890	$ 141,928			$ 628,397	$ 8,831			$ 784,046
Balance (in shares) at Mar. 31, 2020	18,687	2,200