Stock Based Compensation Incentive Stock Option Plan (Details) - shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
PerformanceStockPlan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotYetAwardedInPeriod	0	0	(8,000)

ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotYetAwardedInPeriod

No definition available.

Name:	bro_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotYetAwardedInPeriod
Namespace Prefix:	bro_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration