Schedule II - Condensed Financial Information of Registrant, Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Statements of Cash Flows [Abstract]
Net cash provided by operating activities	$ 74,862	$ 86,680	$ 100,708
Investing activities [Abstract]
Distributions from limited partnerships	14,636	33,396	6,869
Net purchases of property and equipment	(1,470)	(1,953)	(5,439)
Net cash provided by (used in) investing activities	(86,032)	(151,890)	23,651
Financing activities [Abstract]
Dividends paid to shareholders	(5,692)	(5,857)	(16,835)
Repurchase of common shares	(1,782)	(11,501)	(4,596)
Net cash used in financing activities	(7,474)	(17,358)	(21,431)
Increase (decrease) in cash, cash equivalents and restricted cash and cash equivalents	(18,459)	(81,923)	102,098
Cash, cash equivalents and restricted cash and cash equivalents at beginning of year	67,851
Cash, cash equivalents and restricted cash and cash equivalents at end of year	58,301	67,851
Protective Insurance Corporation [Member]
Condensed Statements of Cash Flows [Abstract]
Net cash provided by operating activities	12,350	10,643	14,019
Investing activities [Abstract]
Purchases of investments	(7,795)	(4,967)	(11,435)
Sales or maturities of investments	8,777	3,935	11,213
Distributions from limited partnerships	0	1	0
Net purchases of property and equipment	0	(380)	(3,677)
Net cash provided by (used in) investing activities	982	(1,411)	(3,899)
Financing activities [Abstract]
Dividends paid to shareholders	(5,692)	(5,857)	(16,835)
Repurchase of common shares	(1,782)	(11,501)	(4,596)
Net cash used in financing activities	(7,474)	(17,358)	(21,431)
Increase (decrease) in cash, cash equivalents and restricted cash and cash equivalents	5,858	(8,126)	(11,311)
Cash, cash equivalents and restricted cash and cash equivalents at beginning of year	7,059	15,185	26,496
Cash, cash equivalents and restricted cash and cash equivalents at end of year	$ 12,917	$ 7,059	$ 15,185