Revenue Recognition and Revenue-related Reserves The Companys revenues are derived from the transportation services we provide through the delivery of goods over the duration of a shipment. Upon receipt of the bill of lading, the contract existence criteria is met as evidenced by a legally enforceable agreement between two parties where collectability is probable, thus creating the distinct performance obligation. The Company has elected to expense initial direct costs as incurred because the average shipment cycle is less than one week. The YRC Freight and Regional Transportation segments recognize revenue and substantially all the purchased transportation expense on a gross basis because we direct the use of the transportation service provided and remain responsible for the complete and proper shipment. Inherent within our revenue recognition practices are estimates for revenue associated with shipments in transit and future adjustments to revenue and accounts receivable for billing adjustments and collectability. We record an allowance for doubtful accounts primarily based on historical uncollectible amounts. We also take into account known factors surrounding specific customers and overall collection trends. For the reserve for uncollectible accounts, we primarily use historical write-off experience but may also consider customer-specific factors, overall collection trends and economic conditions as part of our ongoing monitoring of credit. Our process involves performing ongoing credit evaluations of customers, including the market in which they operate and the overall economic conditions. We continually review historical trends and customer specific factors and make adjustments to the allowance for doubtful accounts as appropriate. Our allowance for doubtful accounts totaled $11.1 million and $12.0 million as of December 31, 2018 and 2017 , respectively. Given the nature of our transportation services, future adjustments may arise which creates variability when establishing the transaction price used to recognize revenue. We have a high volume of performance obligations with similar characteristics, therefore we primarily use historical trends to arrive at estimated reserves. For rerate reserves, which are common for LTL carriers, we assign pricing to bills of lading at the time of shipment based primarily on the weight, general classification of the product, the shipping destination and individual customer discounts. This process is referred to as rating. At various points throughout our process, incorrect ratings could be identified based on many factors, including weight and commodity verifications. Although the majority of rerating occurs in the same month as the original rating, a portion occurs during subsequent periods. At December 31, 2018 and 2017 , our financial statements included a rerate reserve as a reduction to Accounts Receivable of $12.5 million and $8.8 million, respectively. For shipments in transit, we record revenue based on the percentage of service completed as of the period end and recognize delivery costs as incurred. The percentage of service completed for each shipment is based on how far along in the shipment cycle each shipment is in relation to standard transit days. Standard transit days are defined as our published service days between origin zip code and destination zip code. The total revenue earned is accumulated for all shipments in transit at a particular period end and recorded as operating revenue. At December 31, 2018 and 2017 , our financial statements included deferred revenue as a reduction to Accounts Receivable of $25.7 million and $28.1 million , respectively. We considered the disclosure requirements for revenue disaggregation guidance in ASC Topic 606 and noted that our segments disaggregate our revenues based on geographic and time-based factors as our Regional Transportation segment carriers operate in a smaller geographic footprint and have a shorter length of haul as compared to our YRC Freight segment. No other criteria listed in the guidance or through our review process was considered to be meaningful for financial statement users. As such, we conclude that no further disaggregation of revenues is necessary.