Nature of Operations (Policies)	12 Months Ended
Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of OperationsBrown & Brown, Inc., a Florida corporation, and its subsidiaries (collectively, “Brown & Brown” or the “Company”) is a diversified insurance agency, wholesale brokerage, insurance programs and services organization that markets and sells to its customers, insurance products and services, primarily in the property, casualty and employee benefits areas. Brown & Brown’s business is divided into four reportable segments: the Retail Segment provides a broad range of insurance products and services to commercial, public and quasi-public entities, professional and individual customers; the National Programs Segment, acting as a managing general agent (“MGA”), provides professional liability and related package products for certain professionals, a range of insurance products for individuals, flood coverage, and targeted products and services designated for specific industries, trade groups, governmental entities and market niches, all of which are delivered through nationwide networks of independent agents, including Brown & Brown retail agents; the Wholesale Brokerage Segment markets and sells excess and surplus commercial insurance, primarily through independent agents and brokers, as well as Brown & Brown Retail offices; and the Services Segment provides insurance-related services, including third-party claims administration and comprehensive medical utilization management services in both the workers’ compensation and all-lines liability arenas, as well as Medicare Set-aside services, Social Security disability and Medicare benefits advocacy services, and claims adjusting services.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2016, the Financial Accountings Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-18, “Statement of Cash Flows (Topic 230)”: Restricted Cash (“ASU 2016-18”), which requires that the Statement of Cash Flows explain the changes during the period of cash and cash equivalents inclusive of amounts categorized as restricted cash. ASU 2016-18 is effective for periods beginning after December 15, 2017. However, the Company elected to early adopt for the reporting period beginning January 1, 2017 under the full retrospective approach for all periods presented. With the adoption of ASU 2016-18, the change in restricted cash is no longer reflected as a change in operating assets and liabilities, and the Statement of Cash Flows details the changes in the balance of cash and cash equivalents inclusive of restricted cash. Net cash provided by operating activities for the years ended December 31, 2015 and 2016 were previously reported as $411.8 million and $375.2 million, respectively. With the retrospective adoption, the net cash provided by operating activities for the years ended December 31, 2015 and 2016 is now reported as $381.8 million and $411.0 million, respectively. The Company reflects cash collected from customers that is payable to insurance companies as restricted cash if segregation of this cash is required by the state of domicile for the office conducting this transaction or if required by contract with the relevant insurance company providing coverage. Cash collected from customers that is payable to insurance companies is reported in cash and cash equivalents if no such restriction is required. In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230)”: Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) (“ASU 2016-15”), which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified and applies to all entities, including both business entities and not-for-profit entities that are required to present a statement of cash flows under Topic 230. ASU 2016-15 will take effect for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017 and early adoption is permitted. The Company is adopting this change effective January 1, 2018 and has evaluated the impact of ASU 2016-15 determining that there is no impact on the Company’s Statement of Cash Flows. The Company already presents cash paid on contingent consideration in business combination as prescribed by ASU 2016-15 and does not, at this time, engage in the other activities being addressed. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share Based Payment Accounting” (“ASU 2016-09”), which amends guidance issued in Accounting Standards Codification (“ASC”) Topic 718, Compensation - Stock Compensation. ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years and early adoption is permitted. The Company adopted the guidance on January 1, 2017, as required. Prior periods have not been adjusted, as the guidance was adopted prospectively. The principal impact is that the tax benefit or expense from stock compensation is now presented in the income tax line of the Statement of Income, whereas the prior treatment was to present this amount as a component of equity on the Balance Sheet. In addition, the tax benefit or expense is now presented as activity in Cash Flow from Operating Activity, rather than the prior presentation as Cash Flow from Financing Activity in the Statement of Cash Flows. The Company also continues to estimate forfeitures of stock grants as allowed by ASU 2016-09. In March 2016, the FASB issued ASU 2016-08, “Principal Versus Agent Considerations (Reporting Revenue Gross Versus Net)” (“ASU 2016-08”) to clarify certain aspects of the principal-versus-agent guidance included in the new revenue standard ASU 2014-09 “Revenue from Contracts with Customers” (“ASU 2014-09”). The FASB issued the ASU in response to concerns identified by stakeholders, including those related to (1) determining the appropriate unit of account under the revenue standard’s principal-versus-agent guidance and (2) applying the indicators of whether an entity is a principal or an agent in accordance with the revenue standard’s control principle. ASU 2016-08 is effective contemporaneous with ASU 2014-09 beginning January 1, 2018. The impact of adopting ASU 2016-08 is not material to the Company. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which provides guidance for accounting for leases. Under ASU 2016-02, the Company will be required to recognize the assets and liabilities for the rights and obligations created by leased assets. ASU 2016-02 will take effect for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company continues to evaluate the impact of this pronouncement with the principal impact being that the present value of the remaining lease payments be presented as a liability on the Balance Sheet as well as an asset of similar value representing the “Right of Use” for those leased properties. As detailed in Note 13 of the 2016 10-K, the undiscounted contractual cash payments remaining on leased properties was $213.2 million as of December 31, 2016 and is $210.4 million as of December 31, 2017 as detailed in “Management’s Discussion and Analysis of Financial Condition and Results of Operations - Liquidity and Capital Resources” and Note 13 “Commitments and Contingencies.” In November 2015, FASB issued ASU No. 2015-17, “Income Taxes (Topic 740) - Balance Sheet Classification of Deferred Taxes” (“ASU 2015-17”), which simplifies the presentation of deferred income taxes by requiring deferred tax assets and liabilities be classified as a single non-current item on the balance sheet. ASU 2015-17 is effective for fiscal years beginning after December 15, 2016 with early adoption permitted as of the beginning of any interim or annual reporting period. The Company adopted the guidance on January 1, 2017, as required. As a result, the Company retrospectively applied the guidance to the 2016 balance sheet by reclassifying $24.6 million from deferred income taxes (asset) to deferred income taxes, net (liability) on the Condensed Consolidated Balance Sheet. This reclassification occurred prior to the passage of the Tax Cuts and Jobs Act of 2017, which had a material impact on the value of deferred tax items. See Note 9 “Income Taxes” for more information. In May 2014, FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“Topic 606”), which provides guidance for revenue recognition. Topic 606 affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets. It supersedes the revenue recognition requirements in Topic 605, “Revenue Recognition,” and most industry-specific guidance. The standard’s core principle is that a company should recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which a company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the current guidance. Specifically, in situations where multiple performance obligations exist within a contract, the use of estimates is required to allocate the transaction price to each separate performance obligation. Historically, approximately 70% of the Company’s commissions and fees are in the form of commissions paid by insurance carriers. These commissions are earned upon the effective date of bound coverage, as no significant performance obligation remains after coverage is bound. The following areas are impacted by the adoption of Topic 606: Installment billing - Prior to the adoption of Topic 606, commission revenues related to installment billings were recognized on the latter of the policy effective date (as indicated in the policy) or the date that the premium was billed to the client (as indicated on the premium invoice), with the exception of our Arrowhead businesses, which follow a policy of recognizing these revenues on the latter of the policy effective date or processed date into our systems, regardless of the billing arrangement. As a result of the adoption of Topic 606, revenue associated with the issuance of policies will be recognized upon the effective date of the associated policy, which means that commission revenues billed on an installment basis will be now recognized earlier than they had been previously resulting in revenue will accrued based upon the completion of the performance obligation and thus creating a current asset for the unbilled revenue until such time as an invoice is generated, typically not to exceed twelve months. The Company does not expect the overall impact of these changes to be significant on a full-year basis, but the timing of recognizing revenue will be impacted among quarters when compared to prior years. Contingent commissions - Prior to the adoption of Topic 606, revenue that was not fixed and determinable because a contingency exists was not recognized until the contingency was resolved. Under Topic 606, the Company must use its judgment to estimate the amount of consideration that will be received such that a significant reversal of revenue is not probable. Contingent commissions represent a form of variable consideration associated with the same performance obligation, which is the placement of coverage, for which we earn core commissions. In connection with the new standard, contingent commissions will be estimated with an appropriate constraint applied and accrued relative to the recognition of the corresponding core commissions. The resulting effect on the timing of recognition of contingent commissions will more closely follow a similar pattern as our core commissions with true-ups recognized when payments are received or as additional information that affects the estimate becomes available. Contingent commissions have averaged approximately 3.6% of the previous year’s total commissions and fees over the last three years and have primarily been received in the first and second quarters of the year. Approximately 30% of the Company’s commissions and fees is in the form of fees, which are predominantly in our National Programs and Services Segments, and to a lesser extent in the large accounts business within our Retail Segment, where we receive fees in lieu of a commission. In accordance with Topic 606, fee revenue from certain agreements will be recognized in earlier periods and others in later periods as compared to our current accounting treatment. The Company does not expect the overall impact of these changes to be significant on a full-year basis, but the timing of recognizing revenue will be impacted among quarters when compared to prior years. Additionally, the Company has evaluated ASC Topic 340 - Other Assets and Deferred Cost (“ASC 340”) which requires companies to defer certain incremental costs to obtain customer contracts, and certain costs to fulfill customer contracts. Incremental cost to obtain - the adoption of ASC 340 will result in the Company deferring certain cost to obtain customer contracts primarily as they relate to commission based compensation plans in the Retail Segment, in which the Company pays an incremental amount of compensation on new business in the first year of the contract. These incremental costs will be deferred and amortized over a 15-year period, which is consistent with the analysis performed on acquired customer accounts and referenced in Note 4 to the Company’s financial statements. Cost to fulfill - the adoption of ASC 340 will result in the Company deferring certain costs to fulfill a contract and recognize these costs as the associated performance obligations are fulfilled. In order for contract fulfillment costs to be deferred under ASC 340, the costs must (1) relate directly to a specific contract or anticipated contract, (2) generate or enhance resources that the Company will use in satisfying its obligations under the contract, and (3) be expected to be recovered through sufficient net cash flows from the contract. The Company does not expect the overall impact of these changes to be significant on a full-year basis, but the timing of recognizing these expenses will be impacted among quarters to better align with the associated revenue. Topic 606 is effective for the Company beginning January 1, 2018. Entities are permitted to adopt the guidance under one of the following methods: the “full retrospective” method, which applies the guidance to each period presented (prior years restated), or the “modified retrospective” method, in which the guidance is only applied to the year of adoption, with the cumulative effect of initially applying the guidance recognized as an adjustment to retained earnings. The Company has elected to follow the modified retrospective method applied to contracts that are not completed as of the date of adoption. The estimated cumulative impact of adopting the standard on January 1, 2018 is an increase in stockholders’ equity of between $70.0 million and $110.0 million. In connection with the implementation of this standard, we expect to modify, and in some instances institute additional accounting procedures, processes and internal controls. Given the relative expected impacts of this standard to our revenue streams, we do not expect that these modifications and additions will materially change our internal controls over financial reporting.

In November 2016, the Financial Accountings Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-18, “Statement of Cash Flows (Topic 230)”: Restricted Cash (“ASU 2016-18”), which requires that the Statement of Cash Flows explain the changes during the period of cash and cash equivalents inclusive of amounts categorized as restricted cash. ASU 2016-18 is effective for periods beginning after December 15, 2017. However, the Company elected to early adopt for the reporting period beginning January 1, 2017 under the full retrospective approach for all periods presented. With the adoption of ASU 2016-18, the change in restricted cash is no longer reflected as a change in operating assets and liabilities, and the Statement of Cash Flows details the changes in the balance of cash and cash equivalents inclusive of restricted cash. Net cash provided by operating activities for the years ended December 31, 2015 and 2016 were previously reported as $411.8 million and $375.2 million, respectively. With the retrospective adoption, the net cash provided by operating activities for the years ended December 31, 2015 and 2016 is now reported as $381.8 million and $411.0 million, respectively. The Company reflects cash collected from customers that is payable to insurance companies as restricted cash if segregation of this cash is required by the state of domicile for the office conducting this transaction or if required by contract with the relevant insurance company providing coverage. Cash collected from customers that is payable to insurance companies is reported in cash and cash equivalents if no such restriction is required.

In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230)”: Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) (“ASU 2016-15”), which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified and applies to all entities, including both business entities and not-for-profit entities that are required to present a statement of cash flows under Topic 230. ASU 2016-15 will take effect for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017 and early adoption is permitted. The Company is adopting this change effective January 1, 2018 and has evaluated the impact of ASU 2016-15 determining that there is no impact on the Company’s Statement of Cash Flows. The Company already presents cash paid on contingent consideration in business combination as prescribed by ASU 2016-15 and does not, at this time, engage in the other activities being addressed.

In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share Based Payment Accounting” (“ASU 2016-09”), which amends guidance issued in Accounting Standards Codification (“ASC”) Topic 718, Compensation - Stock Compensation. ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years and early adoption is permitted. The Company adopted the guidance on January 1, 2017, as required. Prior periods have not been adjusted, as the guidance was adopted prospectively. The principal impact is that the tax benefit or expense from stock compensation is now presented in the income tax line of the Statement of Income, whereas the prior treatment was to present this amount as a component of equity on the Balance Sheet. In addition, the tax benefit or expense is now presented as activity in Cash Flow from Operating Activity, rather than the prior presentation as Cash Flow from Financing Activity in the Statement of Cash Flows. The Company also continues to estimate forfeitures of stock grants as allowed by ASU 2016-09.

In March 2016, the FASB issued ASU 2016-08, “Principal Versus Agent Considerations (Reporting Revenue Gross Versus Net)” (“ASU 2016-08”) to clarify certain aspects of the principal-versus-agent guidance included in the new revenue standard ASU 2014-09 “Revenue from Contracts with Customers” (“ASU 2014-09”). The FASB issued the ASU in response to concerns identified by stakeholders, including those related to (1) determining the appropriate unit of account under the revenue standard’s principal-versus-agent guidance and (2) applying the indicators of whether an entity is a principal or an agent in accordance with the revenue standard’s control principle. ASU 2016-08 is effective contemporaneous with ASU 2014-09 beginning January 1, 2018. The impact of adopting ASU 2016-08 is not material to the Company.

In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which provides guidance for accounting for leases. Under ASU 2016-02, the Company will be required to recognize the assets and liabilities for the rights and obligations created by leased assets. ASU 2016-02 will take effect for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company continues to evaluate the impact of this pronouncement with the principal impact being that the present value of the remaining lease payments be presented as a liability on the Balance Sheet as well as an asset of similar value representing the “Right of Use” for those leased properties. As detailed in Note 13 of the 2016 10-K, the undiscounted contractual cash payments remaining on leased properties was $213.2 million as of December 31, 2016 and is $210.4 million as of December 31, 2017 as detailed in “Management’s Discussion and Analysis of Financial Condition and Results of Operations - Liquidity and Capital Resources” and Note 13 “Commitments and Contingencies.”

In November 2015, FASB issued ASU No. 2015-17, “Income Taxes (Topic 740) - Balance Sheet Classification of Deferred Taxes” (“ASU 2015-17”), which simplifies the presentation of deferred income taxes by requiring deferred tax assets and liabilities be classified as a single non-current item on the balance sheet. ASU 2015-17 is effective for fiscal years beginning after December 15, 2016 with early adoption permitted as of the beginning of any interim or annual reporting period. The Company adopted the guidance on January 1, 2017, as required. As a result, the Company retrospectively applied the guidance to the 2016 balance sheet by reclassifying $24.6 million from deferred income taxes (asset) to deferred income taxes, net (liability) on the Condensed Consolidated Balance Sheet. This reclassification occurred prior to the passage of the Tax Cuts and Jobs Act of 2017, which had a material impact on the value of deferred tax items. See Note 9 “Income Taxes” for more information.

In May 2014, FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“Topic 606”), which provides guidance for revenue recognition. Topic 606 affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets. It supersedes the revenue recognition requirements in Topic 605, “Revenue Recognition,” and most industry-specific guidance. The standard’s core principle is that a company should recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which a company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the current guidance. Specifically, in situations where multiple performance obligations exist within a contract, the use of estimates is required to allocate the transaction price to each separate performance obligation.

Historically, approximately 70% of the Company’s commissions and fees are in the form of commissions paid by insurance carriers. These commissions are earned upon the effective date of bound coverage, as no significant performance obligation remains after coverage is bound. The following areas are impacted by the adoption of Topic 606:

Installment billing - Prior to the adoption of Topic 606, commission revenues related to installment billings were recognized on the latter of the policy effective date (as indicated in the policy) or the date that the premium was billed to the client (as indicated on the premium invoice), with the exception of our Arrowhead businesses, which follow a policy of recognizing these revenues on the latter of the policy effective date or processed date into our systems, regardless of the billing arrangement. As a result of the adoption of Topic 606, revenue associated with the issuance of policies will be recognized upon the effective date of the associated policy, which means that commission revenues billed on an installment basis will be now recognized earlier than they had been previously resulting in revenue will accrued based upon the completion of the performance obligation and thus creating a current asset for the unbilled revenue until such time as an invoice is generated, typically not to exceed twelve months. The Company does not expect the overall impact of these changes to be significant on a full-year basis, but the timing of recognizing revenue will be impacted among quarters when compared to prior years.

Contingent commissions - Prior to the adoption of Topic 606, revenue that was not fixed and determinable because a contingency exists was not recognized until the contingency was resolved. Under Topic 606, the Company must use its judgment to estimate the amount of consideration that will be received such that a significant reversal of revenue is not probable. Contingent commissions represent a form of variable consideration associated with the same performance obligation, which is the placement of coverage, for which we earn core commissions. In connection with the new standard, contingent commissions will be estimated with an appropriate constraint applied and accrued relative to the recognition of the corresponding core commissions. The resulting effect on the timing of recognition of contingent commissions will more closely follow a similar pattern as our core commissions with true-ups recognized when payments are received or as additional information that affects the estimate becomes available. Contingent commissions have averaged approximately 3.6% of the previous year’s total commissions and fees over the last three years and have primarily been received in the first and second quarters of the year.

Approximately 30% of the Company’s commissions and fees is in the form of fees, which are predominantly in our National Programs and Services Segments, and to a lesser extent in the large accounts business within our Retail Segment, where we receive fees in lieu of a commission. In accordance with Topic 606, fee revenue from certain agreements will be recognized in earlier periods and others in later periods

Incremental cost to obtain - the adoption of ASC 340 will result in the Company deferring certain cost to obtain customer contracts primarily as they relate to commission based compensation plans in the Retail Segment, in which the Company pays an incremental amount of compensation on new business in the first year of the contract. These incremental costs will be deferred and amortized over a 15-year period, which is consistent with the analysis performed on acquired customer accounts and referenced in Note 4 to the Company’s financial statements.

Cost to fulfill - the adoption of ASC 340 will result in the Company deferring certain costs to fulfill a contract and recognize these costs as the associated performance obligations are fulfilled. In order for contract fulfillment costs to be deferred under ASC 340, the costs must (1) relate directly to a specific contract or anticipated contract, (2) generate or enhance resources that the Company will use in satisfying its obligations under the contract, and (3) be expected to be recovered through sufficient net cash flows from the contract. The Company does not expect the overall impact of these changes to be significant on a full-year basis, but the timing of recognizing these expenses will be impacted among quarters to better align with the associated revenue.

Topic 606 is effective for the Company beginning January 1, 2018. Entities are permitted to adopt the guidance under one of the following methods: the “full retrospective” method, which applies the guidance to each period presented (prior years restated), or the “modified retrospective” method, in which the guidance is only applied to the year of adoption, with the cumulative effect of initially applying the guidance recognized as an adjustment to retained earnings. The Company has elected to follow the modified retrospective method applied to contracts that are not completed as of the date of adoption. The estimated cumulative impact of adopting the standard on January 1, 2018 is an increase in stockholders’ equity of between $70.0 million and $110.0 million.