Earnings Per Share - Schedule of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Basic Earnings per Share:
Net income attributable to Watsco, Inc. shareholders	$ 113,298	$ 55,092
Basic earnings per share for Common and Class B common stock	$ 2.91	$ 1.39
Diluted Earnings per Share:
Net income attributable to Watsco, Inc. shareholders	$ 113,298	$ 55,092
Diluted earnings per share for Common and Class B common stock	$ 2.90	$ 1.39
Class B Common Stock
Basic Earnings per Share:
Earnings allocated to Watsco, Inc. shareholders – Basic	$ 7,466	$ 3,586
Common Stock
Basic Earnings per Share:
Earnings allocated to Watsco, Inc. shareholders – Basic	95,521	45,452
Common Stock | Class B Common Stock
Basic Earnings per Share:
Net income attributable to Watsco, Inc. shareholders	113,298	55,092
Less: distributed and undistributed earnings allocated to non-vested restricted common stock	10,311	6,054
Earnings allocated to Watsco, Inc. shareholders – Basic	$ 102,987	$ 49,038
Weighted-average common shares outstanding - Basic	35,348,977	35,179,521
Basic earnings per share for Common and Class B common stock	$ 2.91	$ 1.39
Diluted Earnings per Share:
Net income attributable to Watsco, Inc. shareholders	$ 113,298	$ 55,092
Less: distributed and undistributed earnings allocated to non-vested restricted common stock – Diluted	10,297	6,054
Earnings allocated to Watsco, Inc. shareholders – Diluted	$ 103,001	$ 49,038
Weighted-average common shares outstanding - Basic	35,348,977	35,179,521
Effect of dilutive stock options	155,403	150,312
Weighted-average common shares outstanding - Diluted	35,504,380	35,329,833
Diluted earnings per share for Common and Class B common stock	$ 2.90	$ 1.39
Anti-dilutive stock options not included above	143,372	5,911