SCHEDULE II CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments other than subsidiaries [Abstract]
Fixed maturities												$ 437,184	$ 451,809
Limited partnerships												75,458	81,230
Total Investments												660,360	698,112
Cash and cash equivalents	$ 73,538			$ 64,632	$ 64,632			$ 59,297	$ 73,538	$ 64,632	$ 71,549	73,538	64,632	$ 59,297	$ 71,549
Accounts receivable												66,522	98,144
Other assets												11,009	9,413
Total Assets												1,085,771	1,144,247
Liabilities [Abstract]
Total Liabilities												691,273	744,751
Shareholders' equity [Abstract]
Additional paid-in capital												52,946	51,854
Unrealized net gains on investments												38,924	51,840
Foreign exchange adjustment												(1,066)	390
Retained earnings												303,053	294,773	280,003	258,358
Shareholders' equity												394,498	399,496	381,724	346,712
Total liabilities and shareholders' equity												1,085,771	1,144,247
Revenue [Abstract]
Commissions and service fees									5,703	6,430	5,944
Net investment income	3,771	$ 3,014	$ 2,898	2,815	2,599	$ 2,073	$ 2,090	2,294	12,498	9,055	8,770
Net realized losses on investments									(1,261)	14,930	23,515
Total revenue									280,275	292,042	290,972
Expenses [Abstract]
Other									90,573	88,048	85,361
Total expenses									246,323	247,644	236,062
Income before federal income taxes and equity in undistributed income of subsidiaries									33,952	44,398	54,910
Federal income tax benefit									10,669	14,681	18,322
Equity in undistributed income of subsidiaries									(1,687)	7,108	7,995
Net income	3,541	$ 7,780	$ 5,718	6,243	8,246	$ 5,770	$ 9,340	6,361	23,283	29,717	36,588
Condensed Statements of Cash Flows [Abstract]
Net cash provided by operating activities									38,197	30,160	35,907
Investing activities [Abstract]
Distributions from limited partnerships									4,494	1,752	2,528
Net cash used in investing activities									(12,832)	(18,867)	(32,641)
Financing activities [Abstract]
Dividends paid to shareholders									(15,003)	(14,947)	(14,943)
Net cash used in financing activities									(15,003)	(4,947)	(14,943)
Increase (decrease) in cash and cash equivalents									8,906	5,335	(12,252)
Cash and cash equivalents at beginning of year				64,632				59,297	64,632	59,297	71,549
Cash and cash equivalents at end of year	73,538				64,632				73,538	64,632	59,297
Class A [Member]
Shareholders' equity [Abstract]
Common stock												112	112
Class B [Member]
Shareholders' equity [Abstract]
Common stock												529	527
Parent Company [Member]
Assets [Abstract]
Investment in subsidiaries												405,192	415,304
Due from affiliates												2,945	2,762
Investments other than subsidiaries [Abstract]
Fixed maturities												12,181	11,924
Limited partnerships												208	233
Total Investments												12,389	12,157
Cash and cash equivalents	17,934			16,615	16,615			9,848	16,615	16,615	9,848	17,934	16,615	$ 9,848	$ 12,143
Accounts receivable												6,418	5,157
Other assets												21,067	17,905
Total Assets												465,945	469,900
Liabilities [Abstract]
Premiums payable												21,672	27,850
Deposits from insureds												23,484	18,303
Notes payable to bank												20,000	20,000
Other liabilities												6,291	4,251
Total Liabilities												71,447	70,404
Shareholders' equity [Abstract]
Additional paid-in capital												52,946	51,854
Unrealized net gains on investments												38,924	51,840
Foreign exchange adjustment												(1,066)	390
Retained earnings												303,053	294,773
Shareholders' equity												394,498	399,496
Total liabilities and shareholders' equity												465,945	469,900
Revenue [Abstract]
Commissions and service fees									23,523	22,153	21,597
Cash dividends from subsidiaries									20,000	15,000	15,000
Net investment income									120	102	54
Net realized losses on investments									(22)	(27)	(11)
Other									(17)	126	41
Total revenue									43,604	37,354	36,681
Expenses [Abstract]
Salary and related items									17,616	15,543	15,965
Other									7,297	7,978	6,633
Total expenses									24,913	23,521	22,598
Income before federal income taxes and equity in undistributed income of subsidiaries									18,691	13,833	14,083
Federal income tax benefit									(350)	(294)	(348)
Income before equity in undistributed income of subsidiaries									19,041	14,127	14,431
Equity in undistributed income of subsidiaries									4,242	15,590	22,157
Net income									23,283	29,717	36,588
Condensed Statements of Cash Flows [Abstract]
Net cash provided by operating activities									21,841	19,719	15,125
Investing activities [Abstract]
Purchases of long-term investments									(4,792)	(6,398)	(10,322)
Sales or maturities of long-term investments									4,194	5,253	9,982
Distributions from limited partnerships									0	13	0
Net purchases of property and equipment									(4,921)	(6,873)	(1,775)
Other									0	0	(362)
Net cash used in investing activities									(5,519)	(8,005)	(2,477)
Financing activities [Abstract]
Dividends paid to shareholders									(15,003)	(14,947)	(14,943)
Drawings on line of credit									0	10,000	0
Net cash used in financing activities									(15,003)	(4,947)	(14,943)
Increase (decrease) in cash and cash equivalents									1,319	6,767	(2,295)
Cash and cash equivalents at beginning of year				$ 16,615				$ 9,848	16,615	9,848	12,143
Cash and cash equivalents at end of year	$ 17,934				$ 16,615				$ 17,934	$ 16,615	$ 9,848
Parent Company [Member] | Class A [Member]
Shareholders' equity [Abstract]
Common stock												112	112
Parent Company [Member] | Class B [Member]
Shareholders' equity [Abstract]
Common stock												$ 529	$ 527