SCHEDULE II CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments other than subsidiaries [Abstract]
Fixed maturities												$ 521,853	$ 491,904
Limited partnerships												70,806	76,469
Total Investments												795,422	689,818
Cash and cash equivalents	$ 64,680			$ 62,976	$ 62,976			$ 73,538	$ 62,976	$ 62,976	$ 64,632	64,680	62,976	$ 73,538	$ 64,632
Accounts receivable												87,551	64,984
Other assets												11,030	23,779
Total Assets												1,357,016	1,154,137
Liabilities [Abstract]
Short-term borrowings												20,000	20,000
Total Liabilities												938,205	749,792
Shareholders' equity [Abstract]
Additional paid-in capital												55,078	54,286
Unrealized net gains on investments												46,700	34,051
Foreign exchange adjustment												(309)	(831)
Retained earnings												316,700	316,195
Shareholders' equity												418,811	404,345	394,498	399,496
Total liabilities and shareholders' equity												1,357,016	1,154,137
Revenue [Abstract]
Net investment income	5,661	$ 4,027	$ 4,716	3,692	3,982	$ 3,513	$ 3,549	3,440	18,095	14,483	12,498
Net realized gains (losses) on investments	4,152	5,944	3,296	6,294	6,204	7,732	280	9,012	19,686	23,228	(1,261)
Total revenues									371,234	318,997	280,275
Expenses [Abstract]
Other									113,594	89,462	90,573
Total expenses									361,112	275,943	246,323
Federal income tax benefit									(8,201)	14,109	10,669
Equity in undistributed income of subsidiaries									12,469	2,473	(1,687)
Net income	16,476	7,434	(12,343)	6,756	4,864	4,001	5,969	14,112	18,323	28,945	23,283
Condensed Statements of Comprehensive Income [Abstract]
Net income	16,476	$ 7,434	$ (12,343)	6,756	4,864	$ 4,001	$ 5,969	14,112	18,323	28,945	23,283
Unrealized net losses on securities [Abstract]
Unrealized holding net gains (losses) arising during the period									17,340	8,618	(12,639)
Less: reclassification adjustment for net gains included in net income									(4,691)	(13,491)	(277)
Change in unrealized gains (losses) on investments									12,649	(4,873)	(12,916)
Foreign currency translation adjustments									522	235	(1,456)
Other comprehensive income (loss)									13,171	(4,638)	(14,372)
Comprehensive income									31,494	24,307	8,911
Condensed Statements of Cash Flows [Abstract]
Net cash provided by operating activities									93,711	32,368	38,197
Investing activities [Abstract]
Net sales of short-term investments									500	11,258	746
Distributions from limited partnerships									19,230	1,462	4,494
Net purchases of property and equipment									(6,661)	(7,725)	(7,662)
Net cash used in investing activities									(74,347)	(27,362)	(12,832)
Financing activities [Abstract]
Dividends paid to shareholders									(16,302)	(15,803)	(15,003)
Repurchase of common shares									(1,880)	0	0
Net cash used in financing activities									(18,182)	(15,803)	(15,003)
Increase (decrease) in cash and cash equivalents									1,704	(10,562)	8,906
Cash and cash equivalents at beginning of year				62,976				73,538	62,976	73,538	64,632
Cash and cash equivalents at end of year	64,680				62,976				64,680	62,976	73,538
Class A [Member]
Shareholders' equity [Abstract]
Common stock												112	112
Class B [Member]
Shareholders' equity [Abstract]
Common stock												530	532
Baldwin & Lyons, Inc. [Member]
Assets [Abstract]
Investment in subsidiaries												436,879	409,892
Due from affiliates												1,191	3,381
Investments other than subsidiaries [Abstract]
Fixed maturities												22,306	10,166
Limited partnerships												222	205
Total Investments												22,528	10,371
Cash and cash equivalents	26,496			14,995	14,995			17,934	14,995	14,995	17,934	26,496	14,995	$ 17,934	$ 16,615
Accounts receivable												6,833	7,602
Other assets												24,772	25,763
Total Assets												518,699	472,004
Liabilities [Abstract]
Premiums payable												14,046	11,973
Deposits from insureds												60,893	30,087
Short-term borrowings												20,000	20,000
Other liabilities												4,949	5,599
Total Liabilities												99,888	67,659
Shareholders' equity [Abstract]
Additional paid-in capital												55,078	54,286
Unrealized net gains on investments												46,700	34,051
Foreign exchange adjustment												(309)	(831)
Retained earnings												316,700	316,195
Shareholders' equity												418,811	404,345
Total liabilities and shareholders' equity												518,699	472,004
Revenue [Abstract]
Commissions and service fees									18,863	27,736	23,523
Cash dividends from subsidiaries									10,000	20,000	20,000
Net investment income									348	134	120
Net realized gains (losses) on investments									308	(3)	(22)
Other									(106)	(24)	(17)
Total revenues									29,413	47,843	43,604
Expenses [Abstract]
Salary and related items									18,140	17,462	17,616
Other									9,686	10,808	7,297
Total expenses									27,826	28,270	24,913
Income before federal income taxes and equity in undistributed income of subsidiaries									1,587	19,573	18,691
Federal income tax benefit									(2,971)	(69)	(350)
Income after federal income taxes and equity in undistributed income of subsidiaries									4,558	19,642	19,041
Equity in undistributed income of subsidiaries									13,765	9,303	4,242
Net income									18,323	28,945	23,283
Condensed Statements of Comprehensive Income [Abstract]
Net income									18,323	28,945	23,283
Unrealized net losses on securities [Abstract]
Unrealized holding net gains (losses) arising during the period									17,340	8,618	(12,639)
Less: reclassification adjustment for net gains included in net income									(4,691)	(13,491)	(277)
Change in unrealized gains (losses) on investments									12,649	(4,873)	(12,916)
Foreign currency translation adjustments									522	235	(1,456)
Other comprehensive income (loss)									13,171	(4,638)	(14,372)
Comprehensive income									31,494	24,307	8,911
Condensed Statements of Cash Flows [Abstract]
Net cash provided by operating activities									44,998	15,484	21,841
Investing activities [Abstract]
Purchases of long-term investments									(21,365)	(4,000)	(4,792)
Sales or maturities of long-term investments									9,146	3,493	4,194
Net sales of short-term investments									0	2,165	0
Distributions from limited partnerships									298	0	0
Net purchases of property and equipment									(3,394)	(4,278)	(4,921)
Net cash used in investing activities									(15,315)	(2,620)	(5,519)
Financing activities [Abstract]
Dividends paid to shareholders									(16,302)	(15,803)	(15,003)
Repurchase of common shares									(1,880)	0	0
Net cash used in financing activities									(18,182)	(15,803)	(15,003)
Increase (decrease) in cash and cash equivalents									11,501	(2,939)	1,319
Cash and cash equivalents at beginning of year				$ 14,995				$ 17,934	14,995	17,934	16,615
Cash and cash equivalents at end of year	$ 26,496				$ 14,995				$ 26,496	$ 14,995	$ 17,934
Baldwin & Lyons, Inc. [Member] | Class A [Member]
Shareholders' equity [Abstract]
Common stock												112	112
Baldwin & Lyons, Inc. [Member] | Class B [Member]
Shareholders' equity [Abstract]
Common stock												$ 530	$ 532