Business Combination ( Pro Forma and Actual Consolidated Results) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue:
ProAssurance Actual Consolidated Results	$ 281,628	$ 221,742	$ 501,644	$ 418,443
Net income (loss):
ProAssurance Actual Consolidated Results	92,050	(18,099)	99,785	(40,053)
NORCAL Group
Revenue:
ProAssurance Pro Forma Consolidated Results	315,947	305,326	624,423	602,840
Net income (loss):
ProAssurance Pro Forma Consolidated Results	$ 32,926	$ (15,647)	$ 45,326	$ 40,714