Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018
Entity Information [Line Items]
Entity Registrant Name	Protective Insurance Corp
Entity Central Index Key	0000009346
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		14,878,921
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Class A (voting) [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		2,617,659
Class B (nonvoting) [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		12,261,262