Fair Value of Financial Instruments (Details 3) (USD $)	6 Months Ended	12 Months Ended
Sep. 30, 2014	Mar. 31, 2014
TLP \| Credit Facility
Interest Rate Risk
Outstanding debt	$ 252,000,000
Revolving Credit Facility
Interest Rate Risk
Outstanding debt	1,100,000,000	922,000,000
Interest rate (as a percent)	1.91%	1.98%
Interest Rate Risk \| TLP \| Credit Facility
Interest Rate Risk
Outstanding debt	252,000,000
Interest rate (as a percent)	2.66%
Change in interest rate that would result in an increase or decrease of annual interest expense (as a percent)	0.125%
Increase or decrease in annual interest expense	300,000
Interest Rate Risk \| Variable Rate Debt
Interest Rate Risk
Change in interest rate that would result in an increase or decrease of annual interest expense (as a percent)	0.125%	0.125%
Increase or decrease in annual interest expense	$ 1,300,000	$ 1,200,000

Represents the change in amount of annual interest expense due to change in the average interest rate.

No definition available.

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- Definition

Represents the change in amount of annual interest expense that would result from change in the average interest rate.

+ References

No definition available.

+ Details

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- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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- Definition

The effective interest rate at the end of the reporting period.

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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- Details

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