Reconciliation of Effective Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reconciliation of Effective Income Tax Rate [Line Items]
U.S. federal statutory rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefit and other	3.60%	3.50%	4.60%
Excess tax benefits from share-based compensation	(1.80%)	(1.80%)	(8.60%)
Tax effects on foreign income	1.00%	0.20%	0.30%
FDII	(0.10%)	(0.10%)	(0.10%)
Change in valuation allowance	0.20%	0.30%	0.40%
Tax credits and other	(0.40%)	(0.80%)	(0.40%)
Effective income tax rate attributable to Watsco, Inc.	23.50%	22.30%	17.20%
Taxes attributable to non-controlling interest	(2.70%)	(2.60%)	(2.00%)
Effective income tax rate	20.80%	19.70%	15.20%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of reported income tax benefit from difference to income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to foreign-derived intangible income (FDII).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to noncontrolling interest income (loss) exempt from income taxes.

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to nondeductible expense for share-based payment arrangement.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Effective income tax rate reconciliation controlling interest.

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Effective income tax rate reconciliation tax credits and other.

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Reconciliation of Effective Income Tax Rate [Line Items]

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