Long-Term Debt Schedule of Current Value of Long-term Debt (Details) - Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Mar. 31, 2015
Debt Instrument
Long-term Debt	$ 1,059,902	$ 1,058,089
Debt Instrument, Fair Value Disclosure	(7,259)
Debt Instrument, Unamortized Discount (Premium), Net	(2,643)
Long-term Debt, Gross	1,050,000
2.7% Senior Notes [Member]
Debt Instrument
Long-term Debt	256,845	254,993
Debt Instrument, Fair Value Disclosure	(7,259)	(5,462)
Debt Instrument, Unamortized Discount	414
Long-term Debt, Gross	250,000
3.95% Senior Notes [Member]
Debt Instrument
Long-term Debt	249,600	249,577
Debt Instrument, Fair Value Disclosure	0
Debt Instrument, Unamortized Discount	400
Long-term Debt, Gross	250,000
5.625% senior notes
Debt Instrument
Long-term Debt	553,457	$ 553,519
Debt Instrument, Fair Value Disclosure	0
Debt Instrument, Unamortized Premium	(3,457)
Long-term Debt, Gross	$ 550,000

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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 210.5-02.22)

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-Publisher SEC

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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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.

+ References

No definition available.

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- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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- Definition

The amount of debt premium that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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