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	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Significant non-cash investing and financing activities
Other payable issued for agency acquisitions and purchased customer accounts	$ 2	$ 0
Estimated acquisition earn-out payables issued for agency acquisitions	$ 9	$ 20

Other payable issued for agency acquisitions and purchased customer accounts.

No definition available.

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