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	330	330	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	(223)	0	(223)	0		0
Change in unrealized gain (loss) on investments, net of tax	0	(3,121)	0	(3,121)	0		0
Common stock dividends	0	0	(4,229)	(4,229)	0		0
Repurchase of common stock	(45)	0	(190)	(235)	0		$ 0
Repurchase of common stock (in shares)							(11,000)
Restricted stock grants	478	0	0	478	$ 0		$ 0
Restricted stock grants (in shares)					0		5,000
Ending balance at Mar. 31, 2018	55,511	(2,993)	358,651	411,811	$ 112		$ 530
Ending balance (in shares) at Mar. 31, 2018					2,623,000		12,418,000
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	2,748	2,748	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	307	0	307	0		0
Change in unrealized gain (loss) on investments, net of tax	0	8,456	0	8,456	0		0
Common stock dividends	0	0	(1,493)	(1,493)	0		0
Repurchase of common stock	(108)	0	(359)	(468)	$ 0		$ (1)
Repurchase of common stock (in shares)					0	(100)	(25,000)	(24,858)
Restricted stock grants	437	0	0	438	$ 0		$ 1
Restricted stock grants (in shares)					0		20,000
Ending balance at Mar. 31, 2019	$ 55,049	$ 1,416	$ 308,971	$ 366,070	$ 112		$ 522
Ending balance (in shares) at Mar. 31, 2019					2,615,000		12,249,000