Unaudited Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Total	Class A [Member] Common Stock [Member]	Class A [Member]	Class B [Member] Common Stock [Member]	Class B [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption, net of tax | ASU 2016-01 [Member]	$ 0	$ (46,157)	$ 46,157	$ 0	$ 0		$ 0
Cumulative effect of adoption, net of tax | ASU 2018-02 [Member]	0	117	(117)	0	0		0
Beginning balance at Dec. 31, 2017	55,078	46,391	316,700	418,811	$ 112		$ 530
Beginning balance (in shares) at Dec. 31, 2017					2,623,000		12,424,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	2,817	2,817	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	(411)	0	(411)	0		0
Change in unrealized gain (loss) on investments, net of tax	0	(5,147)	0	(5,147)	0		0
Common stock dividends	0	0	(8,456)	(8,456)	0		0
Repurchase of common stock	(234)	0	(1,044)	(1,280)	0		$ (2)
Repurchase of common stock (in shares)							(54,000)
Restricted stock grants	901	0	0	901	$ 0		$ 0
Restricted stock grants (in shares)					0		10,000
Ending balance at Jun. 30, 2018	55,745	(5,207)	356,057	407,235	$ 112		$ 528
Ending balance (in shares) at Jun. 30, 2018					2,623,000		12,380,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption, net of tax | ASU 2018-02 [Member]		117	(117)
Beginning balance at Mar. 31, 2018	55,511	(2,993)	358,651	411,811	$ 112		$ 530
Beginning balance (in shares) at Mar. 31, 2018					2,623,000		12,418,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	2,487	2,487	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	(188)	0	(188)	0		0
Change in unrealized gain (loss) on investments, net of tax	0	(2,026)	0	(2,026)	0		0
Common stock dividends	0	0	(4,227)	(4,227)	0		0
Repurchase of common stock	(188)	0	(854)	(1,044)	$ 0		$ (2)
Repurchase of common stock (in shares)					0		(43,000)
Restricted stock grants	422	0	0	422	$ 0		$ 0
Restricted stock grants (in shares)					0		5,000
Ending balance at Jun. 30, 2018	55,745	(5,207)	356,057	407,235	$ 112		$ 528
Ending balance (in shares) at Jun. 30, 2018					2,623,000		12,380,000
Beginning balance at Dec. 31, 2018	54,720	(7,347)	308,075	356,082	$ 112		$ 522
Beginning balance (in shares) at Dec. 31, 2018					2,615,000		12,254,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	4,283	4,283	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	591	0	591	0		0
Change in unrealized gain (loss) on investments, net of tax	0	14,973	0	14,973	0		0
Common stock dividends	0	0	(2,987)	(2,987)	0		0
Repurchase of common stock	(1,614)	0	(4,858)	(6,487)	$ 0		$ (15)
Repurchase of common stock (in shares)					(3,000)	(2,893)	(371,000)	(371,188)
Restricted stock grants	959	0	0	961	$ 0		$ 2
Restricted stock grants (in shares)					0		49,000
Ending balance at Jun. 30, 2019	54,065	8,217	304,513	367,416	$ 112		$ 509
Ending balance (in shares) at Jun. 30, 2019					2,612,000		11,932,000
Beginning balance at Mar. 31, 2019	55,049	1,416	308,971	366,070	$ 112		$ 522
Beginning balance (in shares) at Mar. 31, 2019					2,615,000		12,249,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	1,535	1,535	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	284	0	284	0		0
Change in unrealized gain (loss) on investments, net of tax	0	6,517	0	6,517	0		0
Common stock dividends	0	0	(1,494)	(1,494)	0		0
Repurchase of common stock	(1,506)	0	(4,499)	(6,020)	$ 0		$ (15)
Repurchase of common stock (in shares)					(3,000)		(346,000)
Restricted stock grants	522	0	0	524	$ 0		$ 2
Restricted stock grants (in shares)					0		29,000
Ending balance at Jun. 30, 2019	$ 54,065	$ 8,217	$ 304,513	$ 367,416	$ 112		$ 509
Ending balance (in shares) at Jun. 30, 2019					2,612,000		11,932,000