Debt Costs (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Debt Disclosure [Abstract]
Interest and debt costs incurred, net of interest capitalized	$ 18,477	$ 13,247	$ 35,431	$ 26,429
Interest costs capitalized	1,101	2,823	2,494	5,767
Total interest and debt costs	$ 19,578	$ 16,070	$ 37,925	$ 32,196

No definition available.

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- Definition

Interest and debt related expenses associated with nonoperating financing activities of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

+ Details

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- Definition

Amount of interest capitalized during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Allowance for Funds Used during Construction
-URI http://asc.fasb.org/extlink&oid=6504829

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

+ Details

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- Definition

Total interest costs incurred during the period and either capitalized or charged against earnings.

+ References

+ Details

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