Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 01, 2018	Jun. 30, 2017
Entity Information [Line Items]
Entity Registrant Name	BALDWIN & LYONS INC
Entity Central Index Key	0000009346
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 266,182,000
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Class A (voting) [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		2,623,109
Class B (nonvoting) [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		12,387,703