GOODWILL AND OTHER INTANGIBLE ASSETS

Goodwill is not amortized, but is evaluated for impairment annually in the fourth quarter of the fiscal year, or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying value.

Circumstances that could trigger an interim impairment test include: a significant adverse change in the business climate or legal factors; an adverse action or assessment by a regulator; unanticipated competition; the loss of key personnel; a change in reporting units; the likelihood that a reporting unit or significant portion of a reporting unit will be sold or otherwise disposed of; and the results of testing for recoverability of a significant asset group within a reporting unit.

A qualitative impairment analysis was performed in the fourth quarter of 2019 to assess whether it is more likely than not that the fair value of the Company’s reporting unit is less than its carrying value. The Company assessed relevant events and circumstances including macroeconomic conditions, industry and market considerations, overall financial performance, entity-specific events, and changes in the Company’s stock price. The Company determined that there was no goodwill impairment in 2019.

A quantitative impairment analysis was performed in the fourth quarter of 2018 and 2017, and the Company estimated the fair value of its reporting unit using an income approach. The income approach requires management to estimate a number of factors for its reporting unit, including projected future operating results, economic projections, anticipated future cash flows, and discount rates. The fair value determined using the income approach was then compared to marketplace fair value data from within a comparable industry grouping for reasonableness. The Company determined that there was no goodwill impairment in 2018 or 2017.

The determination of fair value and the allocation of that value to individual assets and liabilities within the reporting unit requires the Company to make significant estimates and assumptions. These estimates and assumptions primarily include, but are not limited to, the selection of appropriate peer group companies; control premiums appropriate for acquisitions in the industries in which the Company competes; the discount rate; terminal growth rates; and forecasts of revenue, operating income, depreciation and amortization, and capital expenditures. Actual financial results could differ from those estimates due to the inherent uncertainty involved in making such estimates. Changes in assumptions concerning future financial results or other underlying assumptions could have a significant impact on either the fair value of the reporting unit, the amount of the goodwill impairment charge, or both.

Changes in the carrying amount of goodwill consist of the following activity for the years ended December 31, 2019 and 2018 (in thousands):



Balance at December 31, 2017	$	627,392
Acquisitions	5,077
Balance at December 31, 2018	$	632,469
Acquisitions	793,073
Balance at December 31, 2019	$	1,425,542

There was no change in the carrying amount of goodwill for the year ended December 31, 2017.

The carrying amount and accumulated amortization of intangible assets consists of the following as of December 31, 2019 and 2018 (in thousands):



	December 31, 2019			December 31, 2018
Gross intangible assets:
Referral sources	$	438,121		$	257,792
Trademarks/names	44,536			32,000
Other amortizable intangible assets	402			4,151
Total gross intangible assets	483,059			293,943

Accumulated amortization:
Referral sources	(84,295		)	(63,353		)
Trademarks/names	(12,748		)	(8,000		)
Other amortizable intangible assets	(106		)	(2,877		)
Total accumulated amortization	(97,149		)	(74,230		)
Total intangible assets, net	$	385,910		$	219,713

Amortization expense for intangible assets was $26.1 million, $19.6 million and $19.8 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Expected future amortization expense for intangible assets recorded at December 31, 2019, is as follows (in thousands):



2020	$	34,859
2021	32,015
2022	28,338
2023	28,338
2024	28,338
2025 and beyond	234,022
Total	$	385,910

The weighted average amortization period of intangible assets by class and in total as of December 31, 2019 are as follows: 17.1 years for referral sources, 4.2 years for trademarks/names, 1.5 years for other amortizable intangible assets, and 15.9 years for total intangible assets.