Recently Issued Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Mar. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets	$ 82,612	$ 79,393
Total assets	7,144,581	5,537,883
Senior convertible debentures	1,250,178	1,216,313
Junior convertible debentures	198,393	193,936
Long-term line of credit	1,675,423	1,043,156
Total liabilities and stockholder's equity	$ 7,144,581	5,537,883
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets		109,025
Total assets		5,567,515
Senior convertible debentures		1,234,733
Junior convertible debentures		196,304
Long-term line of credit		1,052,000
Total liabilities and stockholder's equity		5,567,515
Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets		(29,632)
Total assets		(29,632)
Senior convertible debentures		(18,420)
Junior convertible debentures		(2,368)
Long-term line of credit		(8,844)
Total liabilities and stockholder's equity		(29,632)
As Adjusted
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets		79,393
Total assets		5,537,883
Senior convertible debentures		1,216,313
Junior convertible debentures		193,936
Long-term line of credit		1,043,156
Total liabilities and stockholder's equity		5,537,883
Accounting Standards Update 2016-09, Forfeiture Rate Component \| Additional Paid-in Capital \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		(2,000)
Accounting Standards Update 2016-09, Forfeiture Rate Component \| Retained Earnings \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		2,000
Accounting Standards Update 2016-09, Forfeiture Rate Component, Share-based Payment Award Component \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income tax assets, net		2,300
Accounting Standards Update 2016-09, Forfeiture Rate Component, Share-based Payment Award Component \| Retained Earnings \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		2,300
Accounting Standards Update 2016-09, Excess Tax Benefit Component \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income tax assets, net		47,200
Accounting Standards Update 2016-09, Excess Tax Benefit Component \| Retained Earnings \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ 47,200

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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