Debt Instruments Maturity Year

No definition available.

Name:	bro_DebtInstrumentsMaturityYear
Namespace Prefix:	bro_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Unsecured Revolving Credit Facility

+ References

No definition available.

+ Details

Name:	bro_UnsecuredRevolvingCreditFacility
Namespace Prefix:	bro_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentPeriodicPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

+ References

+ Details

Name:	us-gaap_UnsecuredLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_FourPointFiveZeroZeroPercentSeniorNotesDueTwoThousandEighteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_UnsecuredSeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_FourPointTwoZeroZeroPercentSeniorNotesDueTwoThousandTwentyFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_FiveYearTermLoanFacilityExpiresInTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_FiveYearTermLoanFacilityExpiresInTwoThousandNinteenCurrentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_FiveYearRevolvingLoanFacilityExpiresInTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_FourPointFiveZeroZeroPercentSeniorNotesDueTwoThousandTwentyNineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bro_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=bro_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AuctionMarketPreferredSecuritiesStockSeriesAxis=bro_SeriesEMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TradingActivityByTypeAxis=bro_MasterAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt - Long-Term Debt Instrument (Additional Information) (Detail) - USD ($)		3 Months Ended	12 Months Ended
	Dec. 21, 2018	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2019	Mar. 11, 2019	Nov. 15, 2018	Jun. 28, 2017	Sep. 18, 2014	Apr. 17, 2014	Sep. 15, 2011
Debt Instrument [Line Items]
Unsecured Revolving Credit Facility		$ 10,000,000.0	$ 350,000,000.0			$ 600,000,000.0	$ 400,000,000.0		$ 800,000,000.0
Unsecured Long-term Debt, Noncurrent		360,000,000.0
Debt Instrument, Periodic Payment	$ 250,000,000.0
Debt Instrument, Annual Principal Payment		1,494,998,000	1,506,990,000
Senior Notes		$ 848,583,000	$ 499,101,000
4.500% senior notes, Series E, quarterly interest payments, balloon due 2018
Debt Instrument [Line Items]
Debt instrument maturity year		2029	2029
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage					4.50%			4.20%
Debt Instrument, Annual Principal Payment		$ 350,000,000.0	$ 500,000,000.0
4.200% senior notes, semi-annual interest payments, net of the unamortized discount, balloon due 2024
Debt Instrument [Line Items]
Debt instrument maturity year		2024	2024
Senior Notes		$ 499,140,000	$ 499,101,000
5-year term-loan facility, periodic interest and principal payments, LIBOR plus up to 1.750%, expires June 28, 2022
Debt Instrument [Line Items]
Line of credit facility, expiration period		5 years	5 years
Line of credit facility, expiration date		Jun. 28, 2022	Jun. 28, 2022
Five Year Term Loan Facility Expires In Two Thousand Ninteen Current [Member]
Debt Instrument [Line Items]
Debt instrument maturity year		2022	2022
5-year revolving-loan facility, periodic interest payments, LIBOR plus up to 1.500%, plus commitment fees up to 0.250%, expires June 28, 2022
Debt Instrument [Line Items]
Line of credit facility, expiration period		5 years	5 years
Line of credit facility, expiration date		Jun. 28, 2022	Jun. 28, 2022
Four Point Five Zero Zero Percent Senior Notes Due Two Thousand Twenty Nine [Member]
Debt Instrument [Line Items]
Senior Notes		$ 350,000,000.0			$ 350,000,000.0
Maximum
Debt Instrument [Line Items]
Debt instrument, variable interest rate		1.75%
Maximum \| Term Loan [Member] \| LIBOR
Debt Instrument [Line Items]
Debt instrument, variable interest rate		1.75%	1.75%
Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate		1.00%
Revolving Credit Facility [Member] \| Maximum
Debt Instrument [Line Items]
Line of Credit Facility, Commitment Fee Percentage		0.25%	0.25%
Revolving Credit Facility [Member] \| Maximum \| LIBOR
Debt Instrument [Line Items]
Debt instrument, variable interest rate		1.50%	1.50%
Term Loan [Member]
Debt Instrument [Line Items]
Unsecured Long-term Debt, Noncurrent	300,000,000.0		$ 300,000,000.0
Term Loan [Member] \| Maximum
Debt Instrument [Line Items]
Unsecured Long-term Debt, Noncurrent	450,000,000.0
Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Unsecured Long-term Debt, Noncurrent	$ 300,000,000.0
Series E [Member] \| Master Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage										4.50%
Subsequent Event [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Two				$ 3,800,000