Operating Revenues	3 Months Ended
Mar. 31, 2018
Operating Revenues
Operating Revenues	4. Operating Revenues Our Solid Waste operating revenues are primarily generated from fees charged for our collection, transfer, disposal, and recycling and resource recovery services, and from sales of commodities by our recycling and landfill gas-to-energy operations. Revenues from our collection operations are influenced by factors such as collection frequency, type of collection equipment furnished, type and volume or weight of the waste collected, distance to the disposal facility or material recovery facility and our disposal costs. Revenues from our landfill operations consist of tipping fees, which are generally based on the type and weight or volume of waste being disposed of at our disposal facilities. Fees charged at transfer stations are generally based on the weight or volume of waste deposited, taking into account our cost of loading, transporting and disposing of the solid waste at a disposal site. Recycling revenues generally consist of tipping fees and the sale of recycling commodities to third parties. The fees we charge for our services generally include our environmental fee, fuel surcharge and regulatory recovery fee, which are intended to pass through to customers direct and indirect costs incurred. We also provide additional services that are not managed through our Solid Waste business, including operations managed by both our Strategic Business Solutions (“WMSBS”) and Energy and Environmental Services (“EES”) organizations, recycling brokerage services, landfill gas-to-energy services and certain other expanded service offerings and solutions. Our revenue from sources other than customer contracts primarily relates to lease revenue associated with compactors and balers. Revenue from these leasing arrangements was not material and represented approximately 1% of total revenue for each of the reported periods. See Note 8 for additional information related to revenue by reportable segment and major lines of business. Revenue Recognition We generally recognize revenue as services are performed or products are delivered. For example, revenue typically is recognized as waste is collected, tons are received at our landfills or transfer stations, or recycling commodities are collected or delivered as product. We bill for certain services prior to performance. Such services include, among others, certain commercial and residential contracts and equipment rentals. These advance billings are included in deferred revenues and recognized as revenue in the period service is provided. Accounts Receivable Accounts receivable, which are recorded when billed, when services are performed or when cash is advanced, are claims against third parties that will generally be settled in cash. The carrying value of our receivables, net of the allowance for doubtful accounts, represents the estimated net realizable value. We estimate our allowance for doubtful accounts based on historical collection trends; type of customer, such as municipal or commercial; the age of outstanding receivables; and existing economic conditions. If events or changes in circumstances indicate that specific receivable balances may be impaired, further consideration is given to the collectability of those balances and the allowance is adjusted accordingly. Past-due receivable balances are written off when our internal collection efforts have been unsuccessful. Deferred Revenues We record deferred revenues when cash payments are received or due in advance of our performance and classify them as current since they are earned within a year and there are no significant financing components. Substantially all our deferred revenues outstanding as of December 31, 2017 were realized as revenues within one to three months, when the related services were performed. Contract Acquisition Costs Our incremental direct costs of obtaining a contract, which consist primarily of sales incentives, are generally deferred and amortized to selling, general and administrative expense over the estimated life of the relevant customer relationship, ranging from 5 to 13 years. Contract acquisition costs that are paid to the customer are deferred and amortized as a reduction in revenue over the contract life. Our contract acquisition costs are classified as current or noncurrent based on the timing of when we expect to recognize amortization and are included in other assets in our Condensed Consolidated Balance Sheet. As of March 31, 2018, we had $136 million of deferred contract costs, of which $107 million were related to deferred sales incentives. During the three months ended March 31, 2018, we amortized $6 million of sales incentives to selling, general and administrative expense and $10 million of other contract acquisition costs as a reduction in revenue. Long-Term Contracts Approximately 30% of our total revenue is derived from contracts with an effective term greater than one year. The consideration for these contracts is variable in nature. The variable elements of these contracts primarily include the number of homes and businesses served and annual rate changes based on consumer price index, fuel prices or other operating costs. Such contracts are generally within our collection, recycling and other lines of business and have a weighted average remaining contract life of approximately four years. We do not disclose the value of unsatisfied performance obligations for these contracts as our right to consideration corresponds directly to the value provided to the customer for services completed to date and all future variable consideration is allocated to wholly unsatisfied performance obligations.

4. Operating Revenues

Our Solid Waste operating revenues are primarily generated from fees charged for our collection, transfer, disposal, and recycling and resource recovery services, and from sales of commodities by our recycling and landfill gas-to-energy operations. Revenues from our collection operations are influenced by factors such as collection frequency, type of collection equipment furnished, type and volume or weight of the waste collected, distance to the disposal facility or material recovery facility and our disposal costs. Revenues from our landfill operations consist of tipping fees, which are generally based on the type and weight or volume of waste being disposed of at our disposal facilities. Fees charged at transfer stations are generally based on the weight or volume of waste deposited, taking into account our cost of loading, transporting and disposing of the solid waste at a disposal site. Recycling revenues generally consist of tipping fees and the sale of recycling commodities to third parties. The fees we charge for our services generally include our environmental fee, fuel surcharge and regulatory recovery fee, which are intended to pass through to customers direct and indirect costs incurred. We also provide additional services that are not managed through our Solid Waste business, including operations managed by both our Strategic Business Solutions (“WMSBS”) and Energy and Environmental Services (“EES”) organizations, recycling brokerage services, landfill gas-to-energy services and certain other expanded service offerings and solutions.

Our revenue from sources other than customer contracts primarily relates to lease revenue associated with compactors and balers. Revenue from these leasing arrangements was not material and represented approximately 1% of total revenue for each of the reported periods.

See Note 8 for additional information related to revenue by reportable segment and major lines of business.

Revenue Recognition

We generally recognize revenue as services are performed or products are delivered. For example, revenue typically is recognized as waste is collected, tons are received at our landfills or transfer stations, or recycling commodities are collected or delivered as product. We bill for certain services prior to performance. Such services include, among others, certain commercial and residential contracts and equipment rentals. These advance billings are included in deferred revenues and recognized as revenue in the period service is provided.

Accounts Receivable

Accounts receivable, which are recorded when billed, when services are performed or when cash is advanced, are claims against third parties that will generally be settled in cash. The carrying value of our receivables, net of the allowance for doubtful accounts, represents the estimated net realizable value. We estimate our allowance for doubtful accounts based on historical collection trends; type of customer, such as municipal or commercial; the age of outstanding receivables; and existing economic conditions. If events or changes in circumstances indicate that specific receivable balances may be impaired, further consideration is given to the collectability of those balances and the allowance is adjusted accordingly. Past-due receivable balances are written off when our internal collection efforts have been unsuccessful.

Deferred Revenues

We record deferred revenues when cash payments are received or due in advance of our performance and classify them as current since they are earned within a year and there are no significant financing components. Substantially all our deferred revenues outstanding as of December 31, 2017 were realized as revenues within one to three months, when the related services were performed.

Contract Acquisition Costs

Our incremental direct costs of obtaining a contract, which consist primarily of sales incentives, are generally deferred and amortized to selling, general and administrative expense over the estimated life of the relevant customer relationship, ranging from 5 to 13 years. Contract acquisition costs that are paid to the customer are deferred and amortized as a reduction in revenue over the contract life. Our contract acquisition costs are classified as current or noncurrent based on the timing of when we expect to recognize amortization and are included in other assets in our Condensed Consolidated Balance Sheet.

As of March 31, 2018, we had $136 million of deferred contract costs, of which $107 million were related to deferred sales incentives. During the three months ended March 31, 2018, we amortized $6 million of sales incentives to selling, general and administrative expense and $10 million of other contract acquisition costs as a reduction in revenue.

Long-Term Contracts

Approximately 30% of our total revenue is derived from contracts with an effective term greater than one year. The consideration for these contracts is variable in nature. The variable elements of these contracts primarily include the number of homes and businesses served and annual rate changes based on consumer price index, fuel prices or other operating costs. Such contracts are generally within our collection, recycling and other lines of business and have a weighted average remaining contract life of approximately four years. We do not disclose the value of unsatisfied performance obligations for these contracts as our right to consideration corresponds directly to the value provided to the customer for services completed to date and all future variable consideration is allocated to wholly unsatisfied performance obligations.