Pension and Employee Benefit Plans, Defined Contribution Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan cost recognized	$ 6.4	$ 5.2	$ 4.7
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Company match	4.50%