Goodwill and Other Intangible Assets - Additional Information (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Intangible Assets by Major Class [Line Items]
Impairment losses on goodwill	¥ 0	¥ 0	¥ 0
Aggregate amortization expenses for intangible assets	32,189	31,752	30,959
Estimated amortization expenses in fiscal 2021	29,076
Estimated amortization expenses in fiscal 2022	26,273
Estimated amortization expenses in fiscal 2023	21,713
Estimated amortization expenses in fiscal 2024	18,004
Estimated amortization expenses in fiscal 2025	14,924
Intangible assets subject to amortization acquired	47,909
Impairment losses on intangible assets	329	¥ 606	¥ 194
Software
Intangible Assets by Major Class [Line Items]
Intangible assets subject to amortization acquired	¥ 16,603
Weighted average amortization period	5 years
Customer Relationships
Intangible Assets by Major Class [Line Items]
Intangible assets subject to amortization acquired	¥ 15,179
Weighted average amortization period	17 years

Intangible Assets by Major Class [Line Items]

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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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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 of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

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