General (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Right-of-use assets	$ 64.9	$ 61.3
Operating lease liabilities, Other current liabilities	12.9
Operating lease liabilities, Other noncurrent liabilities	50.7
Operating leases, right-of-use liabilitiess	63.6
New Accounting Guidance Adopted [Abstract]
Retained earnings	480.1	472.1
Real Estate Leases [Member]
Leases [Abstract]
Right-of-use assets		61.3
Operating lease liabilities, Other current liabilities		12.4
Operating lease liabilities, Other noncurrent liabilities		48.9
Build to Suit Arrangements [Member]
Leases [Abstract]
Right-of-use assets		$ 5.2
Operating leases, right-of-use liabilitiess	$ 5.2
ASU 2014-09 [Member]
New Accounting Guidance Adopted [Abstract]
Retained earnings			$ 0.7
ASU 2016-16 [Member]
New Accounting Guidance Adopted [Abstract]
Retained earnings			$ (8.3)