Goodwill and Intangible Assets - Intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Intangible Assets
Weighted Average Useful Life at Aquisition	10 years 6 months	12 years 10 months 24 days
Gross Carrying Amount	$ 178,987	$ 126,920
Accumulated Amortization	48,084	34,480
Net Carrying Amount	130,903	92,440
Amortization of Intangible Assets	14,675	$ 11,394	$ 10,089
Estimated amortization expense related to the purchased intangible assets
2021	18,292
2022	18,703
2023	18,744
2024	18,310
2025	16,158
Thereafter	40,696
Total	$ 130,903
Customer Relationships
Intangible Assets
Weighted Average Useful Life at Aquisition	10 years 7 months 6 days	13 years
Gross Carrying Amount	$ 176,373	$ 125,520
Accumulated Amortization	46,494	33,679
Net Carrying Amount	$ 129,879	$ 91,841
Trademarks
Intangible Assets
Weighted Average Useful Life at Aquisition	2 years	2 years
Gross Carrying Amount	$ 900	$ 900
Accumulated Amortization	$ 900	431
Net Carrying Amount		$ 469
Technology
Intangible Assets
Weighted Average Useful Life at Aquisition	5 years	5 years
Gross Carrying Amount	$ 500	$ 500
Accumulated Amortization	$ 500	370
Net Carrying Amount		$ 130
Other
Intangible Assets
Weighted Average Useful Life at Aquisition	5 years
Gross Carrying Amount	$ 1,214
Accumulated Amortization	190
Net Carrying Amount	$ 1,024

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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