Income Taxes Other Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Unrecognized Tax Benefits [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 15,958
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	139	$ 4,441	$ 1,492
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	3,303	3,514	9,919
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	5,673	10,078	13,054
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	2,155	1,900	8,570
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(2,200)	(25,046)	(8,521)
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	(8,257)	(155)	0
Unrecognized Tax Benefits	70,787	73,873	92,344	$ 77,892
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	50,462	49,629	62,775
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	(1,605)	(6,862)	$ 0
Previously Unrecognized [Member]
Unrecognized Tax Benefits [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	$ (8,611)
NEW YORK
Unrecognized Tax Benefits [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results		$ 17,053