Income Taxes Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 78,776	$ 62,728	$ 70,787	$ 73,873
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	4,549	7,325	3,303
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	15,070	5,011	5,673
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	(100)	(4,438)	(8,257)
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(2,874)	(15,957)	(2,200)
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	(597)	0	(1,605)
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	67,923	52,772	50,462
Unrecognized Tax Benefits, Period Increase (Decrease)	3,571
Decrease in Unrecognized Tax Benefits is Reasonably Possible	41,462
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 1,937	$ 1,937	$ 2,155