Revenue recognition   The Company's revenue recognition policies are as follows: Operating lease income: The Company's leases have all been determined to be operating leases based on an analysis performed in accordance with ASC 840. Operating lease income is recognized on the straight-line method of accounting, generally from the later of the date the lessee takes possession of the space and it is ready for its intended use or the date of acquisition of the facility subject to existing leases. Accordingly, contractual lease payment increases are recognized evenly over the term of the lease. The periodic difference between lease revenue recognized under this method and contractual lease payment terms is recorded as "Deferred operating lease income receivable," on the Company's Consolidated Balance Sheets. The Company also recognizes revenue from certain tenant leases for reimbursements of all or a portion of operating expenses, including common area costs, insurance, utilities and real estate taxes of the respective property. This revenue is accrued in the same periods as the expense is incurred and is recorded as  Operating lease income  on the Company's Consolidated Statements of Operations. Revenue is also recorded from certain tenant leases that is contingent upon tenant sales exceeding defined thresholds. These rents are recognized only after the defined threshold has been met for the period. Management estimates losses within its operating lease income receivable and deferred operating lease income receivable balances as of the balance sheet date and incorporates an asset-specific component, as well as a general, formula-based reserve based on management's evaluation of the credit risks associated with these receivables. As of December 31, 2014 and 2013 , the allowance for doubtful accounts related to real estate tenant receivables was $1.3 million and $3.4 million , respectively, and the allowance for doubtful accounts related to deferred operating lease income was $2.4 million and $2.4 million , respective