We provide for depreciation and amortization using the straight-line method over the following estimated useful asset lives:



Classification	Estimated Useful Asset Life
Buildings	42 years
Leasehold improvements	Over the shorter of the asset’s useful life or the lease term
Furniture, fixtures, equipment and software	3 to 14 years
Assets held under finance leases	Over the shorter of the asset’s useful life or the lease term

Depreciation expense was $43.1 million, $37.6 million, and $36.2 million in 2023, 2022, and 2021, respectively.

At the time property is retired or otherwise disposed, the asset and related accumulated depreciation are removed from the accounts, and any resulting gain or loss is credited or charged to other income, net.

We consider properties to be assets held for sale when all of the following criteria are met: (i) a formal commitment to a plan to sell a property has been made and exercised; (ii) the property is available for sale in its present condition; (iii) actions required to

complete the sale of the property have been initiated; (iv) sale of the property is probable and we expect the sale will occur within one year; and (v) the property is being actively marketed for sale at a price that is reasonable given its current market value.

Upon designation as an asset held for sale, we record the carrying value of each property at the lower of its carrying value or its estimated fair value, less estimated costs to sell, and depreciation of the property ceases. We had $6.7 million of assets held for sale at December 31, 2023 and 2022. We did not sell any assets classified as held for sale in 2023 and 2022. During the year ended December 31, 2021, we sold assets classified as held for sale with a net book value of $0.4 million, and recorded a net gain of $9.1 million in other income, net.

Where applicable, we capitalize qualifying internal and external costs incurred to develop or obtain software for internal use during the application development stage. Costs incurred during the pre-application development and post-implementation stages are expensed as incurred. We capitalized software and software development costs of $11.9 million and $2.1 million in 2023 and 2022, respectively, and the amounts are recorded in software.

We review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. For assets classified as held and used, impairment may occur if projected undiscounted cash flows are not adequate to cover the carrying value of the assets. In such cases, additional analysis is conducted to determine the amount of the loss to be recognized. The impairment loss is calculated as the difference between the carrying amount of the asset and its estimated fair value. The analysis requires estimates of the amount and timing of projected cash flows and, where applicable, selection of an appropriate discount rate. Such estimates are critical in determining whether any impairment charge should be recorded and the amount of such charge if an impairment loss is deemed necessary. We did not recognize any impairment on property for the years ended December 31, 2023, 2022 and 2021.