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Plan Assets as Percentage of Total Funds (Detail) - Gratuity | Mar. 31, 2018
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Funds managed by insurance company (1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 100.00% | [1]
Funds managed by insurance company (1) | Government Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 76.90% | [1]
Funds managed by insurance company (1) | Debenture and bonds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 17.30% | [1]
Funds managed by insurance company (1) | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 5.50% | [1]
Funds managed by insurance company (1) | Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 0.30% | [1]
Funds managed by insurance company (2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 100.00% | [1]
Funds managed by insurance company (2) | Government Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 18.00% | [1]
Funds managed by insurance company (2) | Debenture and bonds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 28.50% | [1]
Funds managed by insurance company (2) | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 51.60% | [1]
Funds managed by insurance company (2) | Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 1.90% | [1]
Funds managed by trust |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 100.00% |
Funds managed by trust | Government Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 34.20% |
Funds managed by trust | Debenture and bonds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 48.90% |
Funds managed by trust | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 0.00% |
Funds managed by trust | Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Plan asset as percentage of total funds | 16.90% |
[1] | The data pertaining to plan investment assets measured at fair value by level and total at March 31, 2018 are provided separately.

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- Definition 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. + References No definition available. + Details
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- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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