The changes in the carrying amount of goodwill for the nine months ended September 30, 2020 are as follows (in millions):

Balance, as of December 31, 2019
Goodwill	$	7,142
Accumulated impairment losses		(2,814	)
		4,328

Goodwill acquired as part of acquisitions during current year		1
Goodwill allocated to hospitals held for sale		(109	)

Balance, as of September 30, 2020
Goodwill		7,034
Accumulated impairment losses		(2,814	)
	$	4,220

Goodwill is allocated to each identified reporting unit, which is defined as an operating segment or one level below the operating segment (referred to as a component of the entity). Management has determined that the Company’s operating segment meets the criteria to be classified as a reporting unit. At September 30, 2020, after giving effect to 2020 divestiture activity, the Company had approximately $4.2 billion of goodwill recorded.

Goodwill is evaluated for impairment annually and when an event occurs or circumstances change that, more likely than not, reduce the fair value of the reporting unit below its carrying value. The Company performed its last annual goodwill impairment evaluation during the fourth quarter of 2019 using an October 31, 2019 measurement date, which indicated no impairment.

The Company estimates the fair value of the reporting unit using both a discounted cash flow model as well as a market multiple model. The cash flow forecasts are adjusted by an appropriate discount rate based on the Company’s estimate of a market participant’s weighted-average cost of capital. These models are both based on the Company’s best estimate of future revenues and operating costs and are reconciled to the Company’s consolidated market capitalization, with consideration of the amount a potential acquirer would be required to pay, in the form of a control premium, in order to gain sufficient ownership to set policies, direct operations and control management decisions.

While no impairment was indicated in the Company’s annual goodwill evaluation as of the October 31, 2019 measurement date, the reduction in the Company’s fair value and the resulting goodwill impairment charges recorded in 2016 and 2017 reduced the carrying value of the Company’s hospital operations reporting unit to an amount equal to its estimated fair value as of such prior year measurement dates. This increases the risk that future declines in fair value could result in goodwill impairment. The determination of fair value in the Company’s goodwill impairment analysis is based on an estimate of fair value for each reporting unit utilizing known and estimated inputs at the evaluation date. Some of those inputs include, but are not limited to, the most recent price of the Company’s common stock and fair value of long-term debt, estimates of future revenue and expense growth, estimated market multiples, expected capital expenditures, income tax rates, and costs of invested capital. A detailed evaluation of potential impairment indicators was performed as of September 30, 2020, which specifically considered the volatility of the fair market value of the Company’s outstanding senior secured and unsecured notes and common stock during the nine months ended September 30, 2020, as well as declines in patient volumes and net operating revenues resulting from the COVID-19 pandemic. On the basis of available evidence as of September 30, 2020, no indicators of impairment were identified.

Future estimates of fair value could be adversely affected if the actual outcome of one or more of the assumptions described above changes materially in the future, including a decline in or volatility of the Company’s stock price and the fair value of its long-term debt, lower than expected hospital volumes, higher market interest rates or increased operating costs. Such changes impacting the calculation of fair value, the risks of which are amplified by the COVID-19 pandemic, could result in a material impairment charge in the future.

The determination of fair value of the Company’s hospital operations reporting unit as part of its goodwill impairment measurement represents a Level 3 fair value measurement in the fair value hierarchy due to its use of internal projections and unobservable measurement inputs.

No intangible assets other than goodwill were acquired during the nine months ended September 30, 2020. The gross carrying amount of the Company’s other intangible assets subject to amortization was $1 million at both September 30, 2020 and December 31, 2019, and the net carrying amount was less than $1 million at both September 30, 2020 and December 31, 2019. The carrying amount of the Company’s other intangible assets not subject to amortization was $55 million and $63 million at September 30, 2020 and December 31, 2019, respectively. Other intangible assets are included in other assets, net on the Company’s condensed consolidated balance sheets. Substantially all of the Company’s intangible assets are contract-based intangible assets related to operating licenses, management contracts, or non-compete agreements entered into in connection with prior acquisitions.

The gross carrying amount of capitalized software for internal use was approximately $1.1 billion at both September 30, 2020 and December 31, 2019, and the net carrying amount was approximately $270 million and $321 million at September 30, 2020 and December 31, 2019, respectively. The estimated amortization period for capitalized internal-use software is generally three years, except for capitalized costs related to significant system conversions, which is generally eight to ten years. There is no expected residual value for capitalized internal-use software. At September 30, 2020, there was approximately $13 million of capitalized costs for internal-use software that is currently in the development stage and will begin amortization once the software project is complete and ready for its intended use. Amortization expense on capitalized internal-use software was $34 million and $30 million during the three months ended September 30, 2020 and 2019, respectively, and $96 million and $91 million during the nine months ended September 30, 2020 and 2019, respectively. Amortization expense on capitalized internal-use software is estimated to be $30 million for the remainder of 2020, $111 million in 2021, $69 million in 2022, $34 million in 2023, $11 million in 2024, $9 million in 2025 and $6 million thereafter.