pre_text: The following table sets forth our 60-month backlog estimate, by reportable segment, as of December 31, 2019; September 30, 2019; June 30, 2019; March 31, 2019; and December 31, 2018 (in millions). The 60-month backlog estimate includes approximately $1.5 billion as a result of the acquisition of Speedpay, which occurred on May 9, 2019. Dollar amounts reflect foreign currency exchange rates as of each period end. This is a non-GAAP financial measure being presented to provide comparability across accounting periods. We believe this measure provides useful information to investors and others in understanding and evaluating our financial performance. Estimates of future financial results require substantial judgment and are based on several assumptions, as described above. These assumptions may turn out to be inaccurate or wrong for reasons outside of management’s control. For example, our customers may attempt to renegotiate or terminate their contracts for many reasons, including mergers, changes in their financial condition, or general changes in economic conditions in the customer’s industry or geographic location. We may also experience delays in the development or delivery of products or services specified in customer contracts, which may cause the actual renewal rates and amounts to differ from historical experiences. Changes in foreign currency exchange rates may also impact the amount of revenue recognized in future periods. Accordingly, there can be no assurance that amounts included in backlog estimates will generate the specified revenues or that the actual revenues will be generated within the corresponding 60-month period. Additionally, because certain components of Committed Backlog and all of Renewal Backlog estimates are operating metrics, the estimates are not required to be subject to the same level of internal review or controls as contracted but not recognized Committed Backlog.
table: December 31, 2019 September 30, 2019 June 30, 2019 March 31, 2019 December 31, 2018
table: ACI On Premise $1,977 $1,925 $1,880 $1,861 $1,875
table: ACI On Demand 3,855 3,756 3,813 2,290 2,299
table: Total $5,832 $5,681 $5,693 $4,151 $4,174
table: December 31, 2019 September 30, 2019 June 30, 2019 March 31, 2019 December 31, 2018
table: Committed $2,168 $2,003 $2,105 $1,734 $1,832
table: Renewal 3,664 3,678 3,588 2,417 2,342
table: Total $5,832 $5,681 $5,693 $4,151 $4,174
question: Analyse this data from a financial earnings document. What was the difference in committed backlog between December 31 and September 30, 2019?