BASIS OF PRESENTATION (Policies)	3 Months Ended
BASIS OF PRESENTATION (Policies)	Mar. 31, 2020
Basis of Consolidation	Basis of Consolidation Watsco, Inc. (collectively with its subsidiaries, “Watsco,” “we,” “us,” or “our”) was incorporated in Florida in 1956 and is the largest distributor of air conditioning, heating and refrigeration equipment and related parts and supplies (“HVAC/R”) in the HVAC/R distribution industry in North America. The accompanying March 31, 2020 interim condensed consolidated unaudited financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and note disclosures normally included in the annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to those rules and regulations, but we believe the disclosures made are adequate to make the information presented not misleading. In the opinion of management, all adjustments, consisting of normal and recurring adjustments, necessary for a fair presentation have been included in the condensed consolidated unaudited financial statements included herein. These statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our 2019 Annual Report on Form 10-K. The condensed consolidated unaudited financial statements contained in this report include the accounts of Watsco, all of its wholly owned subsidiaries and the accounts of three joint ventures with Carrier Global Corporation (“Carrier”), in each of which Watsco maintains a controlling interest. All significant intercompany balances and transactions have been eliminated in consolidation. The results of operations for the quarter ended March 31, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020. Sales of residential central air conditioners, heating equipment, and parts and supplies are seasonal. Furthermore, profitability can be impacted favorably or unfavorably based on weather patterns, particularly during the Summer and Winter selling seasons. Demand related to the residential central air conditioning replacement market is typically highest in the second and third quarters, and demand for heating equipment is usually highest in the fourth quarter. Demand related to the new construction sectors throughout most of the markets we serve tends to be fairly evenly distributed throughout the year and depends largely on housing completions and related weather and economic conditions.
Use of Estimates	Use of Estimates The preparation of condensed consolidated unaudited financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated unaudited financial statements and the reported amounts of revenues and expenses for the reporting period. Significant estimates include valuation reserves for accounts receivable, net realizable value adjustments to inventories, valuation reserve s for income taxes, reserves related to loss contingencies and the valuation of goodwill, indefinite-lived intangible assets and long-lived assets. While we believe that these estimates are reasonable, actual results could differ from such estimates.
Impact of COVID-19 Pandemic	Impact of COVID-19 Pandemic A novel strain of coronavirus, COVID-19, surfaced in December 2019 and has spread around the world, including to the United States In March 2020, the World Health Organization declared COVID-19 a pandemic. The COVID-19 pandemic has resulted, and is likely to continue to result, in significant economic disruption and has and will likely adversely affect our business and results of operations. Although these disruptions are expected to be temporary, significant uncertainty exists concerning the magnitude of the impact and duration of the COVID-19 pandemic. As we cannot predict the duration or scope of the COVID-19 pandemic, the anticipated negative financial impact to our results of operations cannot be reasonably estimated but could be material and last for an extended period of time.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Financial Instruments—Credit Losses In June 2016, the Financial Accounting Standards Board (“FASB”) issued guidance that modifies the impairment model to utilize an expected loss methodology in place of the incurred loss methodology for financial instruments, including trade receivables, contract assets, long-term receivables and off-balance sheet credit exposures. Under the new standard, an entity will be required to consider a broader range of information to estimate expected credit losses, including historical information, current conditions and a reasonable forecast period, which may result in earlier recognition of certain losses. This guidance is effective for interim and annual periods beginning after December 15, 2019 using a modified retrospective approach. The adoption of this guidance did not have a material impact on our consolidated financial statements. Intangibles—Goodwill and Other In January 2017, the FASB issued guidance to simplify the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under this updated standard, an entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, but the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity also should consider income tax effects from any tax-deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if any. This guidance is effective prospectively and is effective for interim and annual periods beginning after December 15, 2019 with early adoption permitted. The adoption of this guidance did not have a material impact on our consolidated financial statements.