Revenue Recognition Rental income is recognized on a straight-line method under which contractual rent increases are recognized evenly over the lease term. Tenant recovery income includes payments from tenants for real estate taxes, insurance and other property operating expenses and is recognized as revenue in the same period the related expenses are incurred by us. If the lease provides for tenant improvements, we determine whether the tenant improvements are owned by the tenant or us. When we are the owner of the tenant improvements, the tenant is not considered to have taken physical possession or have control of the leased asset until the tenant improvements are substantially complete. Also, when we are the owner of the tenant improvements, any tenant improvements funded by the tenant are treated as lease payments which are deferred and amortized into income over the lease term. When the tenant is the owner of the tenant improvements, we record any tenant improvement allowance funded as a lease inducement and amortize it as a reduction of revenue over the lease term. Revenue is generally recognized on payments received from tenants for early lease terminations upon the effective termination of a tenants lease and when we have no further obligations under the lease. We provide an allowance for doubtful accounts against the portion of tenant accounts receivable including deferred rent receivable, which is estimated to be uncollectible. Tenant accounts receivable in the consolidated balance sheets are shown net of an allowance for doubtful accounts of $310 and $528 as of December 31, 2017 and 2016, respectively. Deferred rent receivable in the consolidated balance sheets is shown net of an allowance for doubtful accounts of $1,557 and $1,694 as of December 31, 2017 and 2016, respectively. For accounts receivable we deem uncollectible, we use the direct write-off method.