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

Asbestos - Summary of Net Unfunded AFFA Liability, Net of Tax (Detail)

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Asbestos - Summary of Net Unfunded AFFA Liability, Net of Tax (Detail) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Mar. 31, 2014
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance $ (811.7)    
Payment received in accordance with AFFA 62.8    
AICF operating costs paid - non claims-handling (1.7) $ (2.5) $ (2.1)
Change in actuarial estimate 2.4 (129.0) (340.3)
Change in claims handling cost estimate 1.2 1.1 $ 0.9
Movement in Income Tax Payable (19.5)    
Other movements (2.1)    
Effect of foreign exchange (2.6)    
Net Unfunded AFFA liability, net of tax, Ending Balance (766.7) (811.7)  
Asbestos Liability [Member]      
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance (1,421.6)    
Asbestos claims paid 113.9    
AICF claims-handling costs incurred (paid) 1.2    
Change in actuarial estimate 2.4    
Change in claims handling cost estimate 1.2    
Effect of foreign exchange 0.7    
Net Unfunded AFFA liability, net of tax, Ending Balance (1,302.2) (1,421.6)  
Insurance Receivables [Member]      
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance 178.6    
Change in actuarial estimate 4.5    
Insurance recoveries (17.2)    
Effect of foreign exchange (0.2)    
Net Unfunded AFFA liability, net of tax, Ending Balance 165.7 178.6  
Deferred Tax Assets [Member]      
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance 405.2    
Movement in Income Tax Payable (18.9)    
Other movements (1.7)    
Effect of foreign exchange 0.3    
Net Unfunded AFFA liability, net of tax, Ending Balance 384.9 405.2  
Other Loan Facilities [Member]      
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance (13.6)    
Funds received from NSW under loan agreement (60.5)    
Funds repaid to NSW under loan agreement 27.3    
Effect of foreign exchange (3.9)    
Net Unfunded AFFA liability, net of tax, Ending Balance (50.7) (13.6)  
Restricted Cash and Investments [Member]      
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance 22.0    
Asbestos claims paid (113.9)    
Payment received in accordance with AFFA 62.8    
AICF claims-handling costs incurred (paid) (1.2)    
AICF operating costs paid - non claims-handling (1.7)    
Insurance recoveries 17.2    
Funds received from NSW under loan agreement 60.5    
Funds repaid to NSW under loan agreement (27.3)    
Other movements (0.7)    
Effect of foreign exchange (0.7)    
Net Unfunded AFFA liability, net of tax, Ending Balance 17.0 22.0  
Other Assets and Liabilities [Member]      
Asbestos Claims [Line Items]      
Net Unfunded AFFA liability, net of tax, Beginning Balance 17.7    
Movement in Income Tax Payable (0.6)    
Other movements 0.3    
Effect of foreign exchange 1.2    
Net Unfunded AFFA liability, net of tax, Ending Balance $ 18.6 $ 17.7