Revenue Recognition Rents that are fixed and determinable are recognized on a straight-line basis over the non-cancellable terms of the leases. Straight-line rental revenue is subject to an evaluation for collectability, and the Company records a provision for losses against rental revenues if collectability of these future rents is not reasonably assured. For the nine months ended September 30, 2018 and 2017 , the Company recognized $7.0 million and $11.4 million , respectively, of straight-line rental revenue. Base rent escalation on leases that are dependent upon increases in the Consumer Price Index (CPI) is recognized when known. For both the nine months ended September 30, 2018 and 2017 , the Company recognized $11.4 million of tenant reimbursements that related to the operations of its entertainment retail centers. Certain reclassifications have been made to the 2017 presentation to conform to the 2018 presentation to combine tenant reimbursements with rental revenue. In addition, most of the Company's tenants are subject to additional rents if gross revenues of the properties exceed certain thresholds defined in the lease agreements (percentage rents). Percentage rents as well as participating interest for those mortgage agreements that contain similar such clauses are recognized at the time when specific triggering events occur as provided by the lease or mortgage agreements. Rental revenue included percentage rents of $5.7 million and $4.7 million for the nine months ended September 30, 2018 and 2017 , respectively. Mortgage and other financing income included participating interest income of $0.7 million for the nine months ended September 30, 2017. No participating interest income was recognized for the nine months ended September 30, 2018. Direct financing lease income is recognized on the effective interest method to produce a level yield on funds not yet recovered. Estimated unguaranteed residual values at the date of lease inception represent management's initial estimates of fair value of the leased assets at the expiration of the lease, not to exceed original cost. Significant assumptions used in estimating residual values include estimated net cash flows over the remaining lease term and expected future real estate values. The Company evaluates on an annual basis (or more frequently, if necessary) the collectability of its direct financing lease receivable and unguaranteed residual value to determine whether they are impaired. A direct financing lease receivable is considered to be impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due according to the existing contractual terms. When a direct financing lease receivable is considered to be impaired, the amount of loss is calculated by comparing the recorded investment to the value determined by discounting the expected future cash flows at the direct financing lease receivable's effective interest rate or to the fair value of the underlying collateral, less costs to sell, if such receivable is collateralized.