Goodwill. The changes in the carrying amount of goodwill for the nine months ended September 30, 2021 were as follows (in thousands):



January 1, 2021 balance	$	272,322
Goodwill acquired during period		42,417
Adjustments related to prior acquisitions		(45	)
Effects of changes in foreign currency exchange rates		(1,448	)
September 30, 2021 balance	$	313,246

Goodwill acquired during the period primarily relates to the acquisition of Tango Telecom Limited and Kitewheel, LLC, as well as the additional investment in MobileCard Holdings, LLC. See Note 5 for discussion regarding these acquisitions.

Other Intangible Assets. Our other intangible assets subject to ongoing amortization consist primarily of acquired customer contracts and software. As of September 30, 2021 and December 31, 2020, the carrying values of these assets were as follows (in thousands):


	September 30, 2021							December 31, 2020
	Gross Carrying Amount		Accumulated Amortization			Net Amount		Gross Carrying Amount		Accumulated Amortization			Net Amount
Acquired customer contracts	$	166,634	$	(111,602	)	$	55,032	$	153,790	$	(105,778	)	$	48,012
Software		177,363		(148,667	)		28,696		166,289		(139,836	)		26,453
Total intangible assets	$	343,997	$	(260,269	)	$	83,728	$	320,079	$	(245,614	)	$	74,465

Other intangible assets as of September 30, 2021 include assets acquired in the Tango Telecom Limited and Kitewheel LLC business acquisitions (see Note 5).

The total amortization expense related to other intangible assets for the third quarters of 2021 and 2020 were $6.5 million and $6.3 million, respectively, and for the nine months ended September 30, 2021 and 2020 were $18.0 million and $18.9 million, respectively. Based on the September 30, 2021 net carrying value of our intangible assets, the estimated total amortization expense for each of the five succeeding fiscal years ending December 31 are: 2021 - $24.4 million; 2022 - $21.0 million; 2023 - $16.7 million; 2024 - $11.1 million; and 2025 - $9.3 million.

Customer Contract Costs. As of September 30, 2021 and December 31, 2020, the carrying values of our customer contract cost assets, related to those contracts with a contractual term greater than one year, were as follows (in thousands):


	September 30, 2021							December 31, 2020
	Gross Carrying Amount		Accumulated Amortization			Net Amount		Gross Carrying Amount		Accumulated Amortization			Net Amount
Customer contract costs	$	97,949	$	(50,700	)	$	47,249	$	87,131	$	(39,893	)	$	47,238

During the second quarter of 2020, we recorded an impairment charge of $10.3 million for the write-off of capitalized customer contract costs related to a discontinued project implementation. This non-cash impairment charge is included primarily in the cost of revenue in our Condensed Consolidated Statements of Income ("Income Statement").

The total amortization expense related to customer contract costs for the third quarters of 2021 and 2020 were $5.3 million and $4.2 million, respectively, and for the nine months ended September 30, 2021 and 2020 were $15.0 million and $12.8 million, respectively.