Basis of Presentation Basis of Presentation (Narrative) (Details) $ in Millions	Sep. 30, 2020 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Carrying value of PPP loans	$ 216.8

Carrying value of Payment Protection Program loans as of balance sheet reporting date

No definition available.

Name:	pre_CarryingvalueofPaymentProtectionProgramloans
Namespace Prefix:	pre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant