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]
Beginning balance at Dec. 31, 2016	$ 54,286	$ 33,220	$ 316,195	$ 404,345	$ 112		$ 532
Beginning balance (in shares) at Dec. 31, 2016					2,623,000		12,461,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	0	0	18,323	18,323	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	522	0	522	0		0
Change in unrealized gain (loss) on investments, net of tax	0	12,649	0	12,649	0		0
Common stock dividends	0	0	(16,302)	(16,302)	0		0
Repurchase of common stock	(360)	0	(1,516)	(1,880)	$ 0		$ (4)
Repurchase of common stock (in shares)					0		(85,000)
Restricted stock grants	1,152	0	0	1,154	$ 0		$ 2
Restricted stock grants (in shares)					0		48,000
Ending balance at Dec. 31, 2017	55,078	46,391	316,700	418,811	$ 112		$ 530
Ending balance (in shares) at Dec. 31, 2017					2,623,000		12,424,000
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
Net income (loss)	0	0	(34,075)	(34,075)	0		0
Foreign currency translation adjustment, net of tax	0	(830)	0	(830)	0		0
Change in unrealized gain (loss) on investments, net of tax	0	(6,868)	0	(6,868)	0		0
Common stock dividends	0	0	(16,835)	(16,835)	0		0
Repurchase of common stock	(832)	0	(3,755)	(4,596)	$ 0		$ (9)
Repurchase of common stock (in shares)					(8,000)		(192,000)
Restricted stock grants	474	0	0	475	$ 0		$ 1
Restricted stock grants (in shares)					0		22,000
Ending balance at Dec. 31, 2018	54,720	(7,347)	308,075	356,082	$ 112		$ 522
Ending balance (in shares) at Dec. 31, 2018					2,615,000		12,254,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	0	0	7,347	7,347	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	645	0	645	0		0
Change in unrealized gain (loss) on investments, net of tax	0	16,071	0	16,071	0		0
Common stock dividends	0	0	(5,857)	(5,857)	0		0
Repurchase of common stock	(2,896)	0	(8,577)	(11,501)	$ (1)		$ (27)
Repurchase of common stock (in shares)					(12,000)	(11,989)	(665,000)	(665,099)
Restricted stock grants	1,525	0	0	1,529	$ 0		$ 4
Restricted stock grants (in shares)					0		87,000
Ending balance at Dec. 31, 2019	$ 53,349	$ 9,369	$ 300,988	$ 364,316	$ 111		$ 499
Ending balance (in shares) at Dec. 31, 2019					2,603,000		11,676,000