Investments in Affiliated Companies (Account Balances and Transactions with Affiliated Companies Accounted for under Equity Method) (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Schedule of Equity Method Investments [Line Items]
Short-term borrowings	¥ 496,093	¥ 464,655
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Accounts receivable, trade	15,516	10,873
Accounts payable, trade	2,568	2,525
Short-term borrowings	22,849	20,650
Capital lease obligations	13,294	10,105
Sales	45,415	31,238	¥ 33,569
Purchases	3,180	1,966	2,259
Lease payments	¥ 7,749	¥ 16,492	¥ 32,291

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of receivables arising from transactions with related parties due within one year or the normal operating cycle, if longer.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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The cash outflow for the obligation for a lease meeting the criteria for capitalization (with maturities exceeding one year or beyond the operating cycle of the entity, if longer).

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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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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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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