Goodwill and Other Intangibles
In accordance with ASC 350, Intangibles – Goodwill and Other, the Company assesses goodwill for impairment annually during the fourth quarter of its fiscal year using October 1 balances or when there is evidence that events or changes in circumstances indicate that the carrying amount of the asset may not be recovered. The Company evaluates goodwill at the reporting unit level using the discounted cash flow valuation model and allocates goodwill to these reporting units using a relative fair value approach. During this assessment, management relies on a number of factors, including operating results, business plans, and anticipated future cash flows. The Company has identified its reportable segments, ACI On Premise and ACI On Demand, as the reporting units.
The key assumptions used in the discounted cash flow valuation model include discount rates, growth rates, cash flow projections and terminal value rates. Discount rates, growth rates, and cash flow projections are the most sensitive and susceptible to change, as they require significant management judgment. Discount rates are determined by using a weighted average cost of capital (“WACC”). The WACC considers market and industry data as well as company-specific risk factors. Operational management, considering industry and company-specific historical and projected data, develops growth rates and cash flow projections for each  flow estimates beyond the last projected period, assuming a constant WACC and low, long-term growth rates. If the recoverability test indicates potential impairment, the Company calculates an implied fair value of goodwill for the reporting unit. The implied fair value of goodwill is determined in a manner similar to how goodwill is calculated in a business combination. If the implied fair value of goodwill exceeds the carrying value of goodwill assigned to the reporting unit, there is no impairment. If the carrying value of goodwill assigned to the reporting unit exceeds the implied fair value of the goodwill, an impairment charge is recorded to write down the carrying value. The calculated fair value substantially exceeded the current carrying value for all reporting units for all periods.
Changes in the carrying amount of goodwill attributable to each reporting unit during the year ended December 31, 2019, were as follows (in thousands):
(1) Goodwill from acquisitions relates to the goodwill recorded for the acquisition of E Commerce Group Products, Inc. ("ECG"), along with ECG's subsidiary, Speedpay, Inc. (collectively referred to as "Speedpay") and Walletron, Inc. ("Walletron"), as discussed in Note 3, Acquisition. The purchase price allocations for Speedpay and Walletron are preliminary as of December 31, 2019, and are subject to future changes during the maximum one-year measurement period.
Other intangible assets, which include customer relationships and trademarks and trade names, are amortized using the straight-line method over periods ranging from three years to 20 years. The Company reviews its other intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable.
Table:
 | ACI On Demand | ACI On Premise | Total
Gross Balance, prior to December 31, 2018 | $ 183,783 | $ 773,340 | $ 957,123
Total impairment prior to December 31, 2018 | — | (47,432) | (47,432 )
Balance, December 31, 2018 | 183,783 | 725,908 | 909,691
Goodwill from acquisitions (1) | 370,834 | — | 370,834
Balance, December 31, 2019 | $554,617 | $725,908 | $1,280,525


Question: How did the company amortize other intangible assets?
Answer: using the straight-line method over periods ranging from three years to 20 years.