v3.25.3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Leasing Operations and Other Expense, Net (Details) ft² in Thousands, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 29, 2024 USD ($) ft²	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Oct. 31, 2024 USD ($) installment
Asset Acquisition [Line Items]
Building occupied (as a percent)	0.30
Payments to acquire land and building				$ 246.2	$ 509.6
Current portion		$ 5.9		5.9		$ 4.5
Non-current portion		36.7		36.7		18.5
Total deferred lease income		42.6		42.6		$ 23.0
Lease income		4.3	$ 6.6	13.3	16.4
Less:
Property operating expenses		1.6	2.5	4.4	6.7
Depreciation and amortization expense		2.7	5.4	14.2	14.3
Other expense from leasing operations		0.0	(1.3)	(5.3)	(4.6)
Amortization expense		$ 31.8	10.3	$ 75.5	31.5
Property occupied (as a percent)		0.50		0.50
Building Tenant
Asset Acquisition [Line Items]
Consideration for the early termination of the lease							$ 48.0
Number of equal installments of buyout payment \| installment							2
Arlington Office Tower
Asset Acquisition [Line Items]
Payments to acquire land and building	$ 343.0
Total property and equipment, net and intangible assets	343.0
Arlington Office Tower \| Land
Asset Acquisition [Line Items]
Property and equipment, net	17.2
Arlington Office Tower \| Building
Asset Acquisition [Line Items]
Property and equipment, net	224.5
Arlington Office Tower \| Land and building improvements
Asset Acquisition [Line Items]
Property and equipment, net	27.5
Acquired above-market leases
Less:
Amortization expense		$ 1.0	$ 2.9	$ 3.0	$ 7.8
Acquired above-market leases \| Arlington Office Tower
Asset Acquisition [Line Items]
Intangible assets, net	41.7
Acquired in-place leases \| Arlington Office Tower
Asset Acquisition [Line Items]
Intangible assets, net	$ 32.1
Arlington, VA
Asset Acquisition [Line Items]
Rentable square feet \| ft²	550

Asset Acquisition, Assets Acquired and Liabilities Assumed, Net

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COSTAR GROUP, INC. 10-Q