Stock Based Compensation Details (Details)	Dec. 31, 2017 shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
MaximumNumberOfSharesAvailableToBeGrantedUnderAwardStockPlan	14,400,000

MaximumNumberOfSharesAvailableToBeGrantedUnderAwardStockPlan

No definition available.

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Namespace Prefix:	bro_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant