Goodwill and Intangible Assets - Amortization (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Intangible assets
Amortization expense	$ 16,492	$ 18,301	$ 50,271	$ 53,262
Depreciation and amortization expense
Intangible assets
Amortization expense	$ 16,500	$ 18,300	$ 50,300	$ 53,300

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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