Stock Based Compensation Summary (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense	$ 93,008	$ 92,927	$ 66,245
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense	8,347	9,403	11,584
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense	52,049	52,670	45,975
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Employee Stock Ownership Plan (ESOP), Compensation Expense	696	729	673
Rabbi trust [Domain]
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense	26	25	201
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense	1,400	1,150	1,550
Key Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Deferred Compensation Arrangement with Individual, Compensation Expense	3,924	2,766	1,056
Subsidiaries [Member] \| Management Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Deferred Compensation Arrangement with Individual, Compensation Expense	$ 26,566	$ 26,184	$ 5,206

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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