During the year ended January 31, 2020, the Company recorded $711.5 million of acquired identified intangible assets as a result of the Acquisition of WageWorks. For further information about these acquired identified intangible assets, see Note 3—Business Combination.

During the years ended January 31, 2020 and 2019, the Company capitalized the following amounts to acquire the rights to act as a custodian of HSA portfolios:

The Company has determined the acquired HSA portfolios to have a useful life of 15 years. The assets are being amortized using the straight-line amortization method, which has been determined to be appropriate to reflect the pattern over which the economic benefits of existing assets are realized.

During the years ended January 31, 2020, 2019 and 2018, the Company capitalized software development costs of $24.1 million, $9.3 million and $8.1 million, respectively, related to significant enhancements and upgrades to its technology-enabled services platforms.

The gross carrying amount and associated accumulated amortization of intangible assets is as follows as of January 31, 2020 and January 31, 2019:


(in thousands)	January 31, 2020		January 31, 2019
Amortizable intangible assets:
Software and software development costs	$	76,221	$	44,835
Acquired HSA portfolios	92,770		85,110
Acquired customer relationships	601,381		2,882
Acquired developed technology	96,925		—
Acquired trade names	12,300		—
Amortizable intangible assets, gross	879,597		132,827
Accumulated amortization	(98,851)		(53,161)
Total amortizable intangible assets, net	780,746		79,666
Acquired in process software development costs	2,533		—
Total intangible assets, net	$	783,279	$	79,666

During the years ended January 31, 2020, 2019 and 2018, the Company expensed a total of $23.8 million, $13.7 million and $12.2 million, respectively, in software development costs primarily related to the post-implementation and operation stages of its proprietary software.

Amortization expense for the years ended January 31, 2020, 2019, and 2018 was $46.5 million, $14.7 million and $13.2 million, respectively. Estimated amortization expense for the years ending January 31 is as follows:


Year ending January 31, (in thousands)
2021	$	90,868
2022	83,476
2023	71,804
2024	62,622
2025	55,810
Thereafter	416,166
Total	$	780,746

During the year ended January 31, 2020, the Company recorded $1.33 billion of goodwill from the Acquisition of WageWorks. For further information about the resulting goodwill, see Note 3—Business Combination. There were no other changes to the goodwill carrying value during the years ended January 31, 2020, 2019, and 2018.