Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Supplemental Cash Flow Elements [Abstract]
Deferred employer only payroll tax payments, CARES Act	$ 31.1

Social security tax, employer, deferral, CARES Act.

No definition available.

Name:	bro_SocialSecurityTaxEmployerDeferralCARESAct
Namespace Prefix:	bro_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration