GOODWILL AND OTHER INTANGIBLE ASSETS

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill is recorded as a result of business combinations. Activity in goodwill for the years ended December 31, 2018 and 2019 is provided below (in thousands):



Balance as of December 31, 2017	$256,776
Goodwill acquired through the acquisition of Imaging Services Company of New York, LLC	2,692
Goodwill acquired through the acquisition of certain assets of MemorialCare Medical Foundation	545
Goodwill transferred to assets held for sale	(1,059	)
Goodwill acquired through the acquisition of Women's Imaging Specialists in Healthcare	4268
Goodwill acquired through the acquisition of Valley Metabolic Imaging	1,469
Goodwill acquired through the acquisition of Sierra Imaging Associates	1,147
Goodwill disposed through the sale of plastic surgery unit	(80	)
Goodwill acquired through the acquisition of Washington Heights Medical Management	2,303
Goodwill acquired through the acquisition of Medical Arts Radiological Group, P.C.	41,469
Goodwill acquired through the acquisition of Arcadia Radiology Imaging Services, LLC	2,582
Goodwill acquired through the acquisition of Southern California Diagnostic Imaging, Inc.	41
Goodwill acquired through the acquisition of Orange County Diagnostics Imaging Center, Inc.	3,618
Goodwill acquired through assuming operational control of New Jersey Imaging Network, LLC	106,122
Goodwill impaired in the Imaging On Call reporting unit	(3,800	)
Balance as of December 31, 2018	418,093
Adjustments to our preliminary allocation of the purchase price of Medical Arts Radiological Group, P.C.	722
Goodwill acquired through the acquisition of certain assets of Dignity Health	1
Goodwill acquired through the acquisition of certain assets of West Valley Imaging Center, LLC	2,490
Goodwill disposed through sale of assets	(123	)
Goodwill acquired by Lenox Hill Radiology through the membership purchase of HVRA	3,125
Goodwill acquired through the acquisition of certain assets of Kern Radiology, Inc.	10,507
Goodwill acquired through the acquisition of certain assets of Zilkha Radiology, Inc.	2,577
Goodwill acquired through the acquisition of certain assets of Ramic Mahwah, LLC	231
Goodwill acquired through the acquisition of GSRN	2,021
Goodwill acquired through the acquisition of Nulogix	1,337
Balance as of December 31, 2019	$440,981

The amount of goodwill from these acquisitions that is deductible for tax purposes as of December 31, 2019 is $160.5 million.

Other intangible assets are primarily related to our business combinations and software development. They include the estimated fair values of such items as service agreements, customer lists, covenants not to compete, acquired technologies, and trade names.

Total amortization expense was $3.1 million, $2.7 million, and $2.6 million for the years ended December 31, 2019, 2018 and 2017, respectively. Intangible assets are amortized using the straight-line method over their useful life determined at acquisition. Management service agreements are amortized over 25 years using the straight line method. Software development is capitalized and amortized over the useful life of the software when placed into service. Trade names are reviewed annually for impairment.

The following table shows annual amortization expense, by asset classes that will be recorded over the next five years (in thousands):



	2020		2021		2022		2023		2024		Thereafter		Total		Weighted average amortization period remaining in years
Management Service Contracts	$	2,287	$	2,287	$	2,287	$	2,287	$	2,287	$	15,820	$	27,255	11.9
Covenant not to compete and other contracts	759		699		650		537		129		142		2,916		4.4
Developed Technology	244		244		142		—		—		—		630		2.6
Trade Names amortized	142		69		69		61		58		219		618		8.4
Trade Names indefinite life	—		—		—		—		—		11,270		11,270		—
Software in development	—		—		—		—		—		305		305		—
Total Annual Amortization	$	3,432	$	3,299	$	3,148	$	2,885	$	2,474	$	27,756	$	42,994