•Branded postpaid customers generally include customers who are qualified to pay after receiving wireless communications services utilizing phones, wearables, DIGITS, or other connected devices which includes tablets and SyncUP DRIVE™;

•Branded prepaid customers generally include customers who pay for wireless communications services in advance. Our branded prepaid customers include customers of T-Mobile and Metro by T-Mobile; and

•Wholesale customers include Machine-to-Machine (“M2M”) and Mobile Virtual Network Operator (“MVNO”) customers that operate on our network but are managed by wholesale partners.

Branded postpaid service revenues, including branded postpaid phone revenues and branded postpaid other revenues, were as follows:


	Year Ended December 31,
(in millions)	2019		2018		2017
Branded postpaid service revenues

Branded postpaid phone revenues	$	21,329	$	19,745	$	18,371
Branded postpaid other revenues	1,344		1,117		1,077

Total branded postpaid service revenues	$	22,673	$	20,862	$	19,448

We operate as a single operating segment. The balances presented within each revenue line item in our Consolidated Statements of Comprehensive Income represent categories of revenue from contracts with customers disaggregated by type of product and service. Service revenues also include revenues earned for providing value added services to customers, such as handset insurance services. Revenue generated from the lease of mobile communication devices is included within Equipment revenues in our Consolidated Statements of Comprehensive Income.


	Year Ended December 31,
(in millions)	2019		2018		2017
Equipment revenues from the lease of mobile communication devices	$	599	$	692	$	877

The opening and closing balances of our contract asset and contract liability balances from contracts with customers as of December 31, 2018 and December 31, 2019, were as follows:


(in millions)	Contract Assets		Contract Liabilities

Balance as of December 31, 2018	$	51	$	645
Balance as of December 31, 2019	63		560

Change	$	12	$	(85)

Contract assets primarily represent revenue recognized for equipment sales with promotional bill credits offered to customers that are paid over time and are contingent on the customer maintaining a service contract. The change in the contract asset balance includes customer activity related to new promotions, offset by billings on existing contracts and impairment which is recognized as bad debt expense. The current portion of our Contract Assets of approximately $50 million and $51 million as of December 31, 2019 and 2018, respectively, was included in Other current assets in our Consolidated Balance Sheets.

Contract liabilities are recorded when fees are collected, or we have an unconditional right to consideration (a receivable) in advance of delivery of goods or services. The change in contract liabilities is primarily related to the migration of customers to unlimited rate plans. Contract liabilities are included in Deferred revenue in our Consolidated Balance Sheets.


	Year Ended December 31,
(in millions)	2019		2018
Amounts included in the beginning of year contract liability balance	$	643	$	710

As of December 31, 2019, the aggregate amount of transaction price allocated to remaining service performance obligations for branded postpaid contracts with promotional bill credits that result in an extended service contract is $237 million. We expect to recognize this revenue as service is provided over the extended contract term in the next 24 months.

Certain of our wholesale, roaming and other service contracts include variable consideration based on usage. This variable consideration has been excluded from the disclosure of remaining performance obligations. As of December 31, 2019, the aggregate amount of the contractual minimum consideration for wholesale, roaming and other service contracts is $1.3 billion, $894 million and $791 million for 2020, 2021 and 2022 and beyond, respectively. These contracts have a remaining duration ranging from less than one year to ten years.

Information about remaining performance obligations that are part of a contract that has an original expected duration of one year or less have been excluded from the above, which primarily consists of monthly service contracts.

The total balance of deferred incremental costs to obtain contracts was $906 million and $644 million as of December 31, 2019 and 2018, respectively. Deferred contract costs incurred to obtain postpaid service contracts are amortized over a period of 24 months. The amortization period is monitored to reflect any significant change in assumptions. Amortization of deferred contract costs is included in Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income and was $604 million and $267 million for the years ended December 31, 2019 and 2018, respectively.

The deferred contract cost asset is assessed for impairment on a periodic basis. There were no impairment losses recognized on deferred contract cost assets for the years ended December 31, 2019 and 2018.