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 (loss)	0	0	(9,508)	(9,508)	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	(209)	0	(209)	0		0
Change in unrealized gain (loss) on investments, net of tax	0	(6,298)	0	(6,298)	0		0
Common stock dividends	0	0	(12,652)	(12,652)	0		0
Repurchase of common stock	(484)	0	(2,131)	(2,620)	0		$ (5)
Repurchase of common stock (in shares)							(112,000)
Restricted stock grants	521	0	0	521	$ 0		$ 0
Restricted stock grants (in shares)					0		13,000
Ending balance at Sep. 30, 2018	55,115	(6,156)	338,449	388,045	$ 112		$ 525
Ending balance (in shares) at Sep. 30, 2018					2,623,000		12,325,000
Beginning balance at Jun. 30, 2018	55,745	(5,207)	356,057	407,235	$ 112		$ 528
Beginning balance (in shares) at Jun. 30, 2018					2,623,000		12,380,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	0	0	(12,325)	(12,325)	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	202	0	202	0		0
Change in unrealized gain (loss) on investments, net of tax	0	(1,151)	0	(1,151)	0		0
Common stock dividends	0	0	(4,196)	(4,196)	0		0
Repurchase of common stock	(250)	0	(1,087)	(1,340)	$ 0		$ (3)
Repurchase of common stock (in shares)					0		(58,000)
Restricted stock grants	(380)	0	0	(380)	$ 0		$ 0
Restricted stock grants (in shares)					0		3,000
Ending balance at Sep. 30, 2018	55,115	(6,156)	338,449	388,045	$ 112		$ 525
Ending balance (in shares) at Sep. 30, 2018					2,623,000		12,325,000
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 (loss)	0	0	3,576	3,576	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	402	0	402	0		0
Change in unrealized gain (loss) on investments, net of tax	0	16,539	0	16,539	0		0
Common stock dividends	0	0	(4,429)	(4,429)	0		0
Repurchase of common stock	(2,590)	0	(7,669)	(10,283)	$ 0		$ (24)
Repurchase of common stock (in shares)					(6,000)	(6,520)	(595,000)	(595,326)
Restricted stock grants	1,540	0	0	1,543	$ 0		$ 3
Restricted stock grants (in shares)					0		80,000
Ending balance at Sep. 30, 2019	53,670	9,594	299,553	363,430	$ 112		$ 501
Ending balance (in shares) at Sep. 30, 2019					2,609,000		11,739,000
Beginning balance at Jun. 30, 2019	54,065	8,217	304,513	367,416	$ 112		$ 509
Beginning balance (in shares) at Jun. 30, 2019					2,612,000		11,932,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	0	0	(707)	(707)	$ 0		$ 0
Foreign currency translation adjustment, net of tax	0	(189)	0	(189)	0		0
Change in unrealized gain (loss) on investments, net of tax	0	1,566	0	1,566	0		0
Common stock dividends	0	0	(1,442)	(1,442)	0		0
Repurchase of common stock	(976)	0	(2,811)	(3,796)	$ 0		$ (9)
Repurchase of common stock (in shares)					(3,000)		(224,000)
Restricted stock grants	581	0	0	582	$ 0		$ 1
Restricted stock grants (in shares)					0		31,000
Ending balance at Sep. 30, 2019	$ 53,670	$ 9,594	$ 299,553	$ 363,430	$ 112		$ 501
Ending balance (in shares) at Sep. 30, 2019					2,609,000		11,739,000