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Minority Investments - Additional Information (Detail) $ in Thousands |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 11, 2016 USD ($) | Mar. 31, 2016 USD ($) | Mar. 31, 2017 USD ($) power_grid | Mar. 31, 2016 USD ($) | Mar. 31, 2015 USD ($)
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |
Proceeds from sale of minority interests |  |  | $ 325 | $ 3,092 | $ 0
Tres Amigas |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |
Number of commonly interconnected power grids | power_grid |  |  | 3 |  |
Equity method investment, aggregate cost |  |  | $ 5,400 |  |
Impairment charge on investment |  |  |  | $ 700 |
Percentage of investment sold | 100.00% |  |  |  |
Minority share investment sold, amount | $ 600 |  |  |  |
Proceeds from sale of minority interests |  | $ 300 | $ 300 |  |

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- Definition This element represents the aggregate cost of investments accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25351-111560 + Details
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- Definition The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585 + Details
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