v3.19.2
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2019
Aug. 05, 2019
Document Information [Line Items]    
Document Type 10-Q  
Document Period End Date Jun. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Entity Registrant Name WATSCO INC  
Entity Central Index Key 0000105016  
Entity Filer Category Large Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Shell Company false  
Entity File Number 1-5581  
Entity Small Business false  
Entity Incorporation, State or Country Code FL  
Entity Emerging Growth Company false  
Document Quarterly Report true  
Document Transition Report false  
Entity Address, State or Province FL  
Entity Tax Identification Number 59-0778222  
Entity Address, Address Line One 2665 South Bayshore Drive  
Entity Address, City or Town Miami  
Entity Address, Postal Zip Code 33133  
City Area Code 305  
Local Phone Number 714-4100  
Entity Address, Address Line Two Suite 901  
Common Stock [Member]    
Document Information [Line Items]    
Trading Symbol WSO  
Security Exchange Name NYSE  
Title of 12(b) Security Common stock, $0.50 par value  
Entity Common Stock, Shares Outstanding   32,613,520
Common Class B [Member]    
Document Information [Line Items]    
Trading Symbol WSOB  
Security Exchange Name NYSE  
Title of 12(b) Security Class B common stock, $0.50 par value  
Entity Common Stock, Shares Outstanding   5,446,199