Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Loss (Detail)

v3.20.1
Accumulated Other Comprehensive Loss (Detail) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Cash flow hedges   $ (0.1) $ 0.0
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance $ 974.4 (221.5) (212.2)
Other comprehensive gain (loss) 31.8    
Ending balance 1,035.3 974.4 (221.5)
Accumulated Other Comprehensive Loss [Member]      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance (30.3) (1.3) (2.2)
Ending balance (62.1) (30.3) $ (1.3)
Cash Flow Hedges [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Cash flow hedges 0.0    
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance 0.2    
Ending balance 0.2 0.2  
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Cash flow hedges 0.8    
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Ending balance 0.8    
Foreign Currency Translation Adjustments [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Cash flow hedges (32.6)    
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance (30.5)    
Ending balance $ (63.1) $ (30.5)