Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Summary of Significant Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024
Significant non-cash investing and financing activities
Other payable issued for agency acquisitions and purchased customer accounts	$ 10	$ 7
Estimated acquisition earn-out payables issued for agency acquisitions	$ 17	$ 19

Other payable issued for agency acquisitions and purchased customer accounts.

No definition available.

Name:	bro_OtherPayableIssuedForAgencyAcquisitionsAndPurchasedCustomerAccounts
Namespace Prefix:	bro_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration