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

Long-Term Debt - Additional Information (Detail)

v2.4.0.8
Long-Term Debt - Additional Information (Detail) (USD $)
12 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Long Term Debt And Equity Financings [Line Items]    
Amounts drawn under the combined facilities $ 0  
Weighted average interest rate on total outstanding debt      
Weighted average term of debt facilities 2 years 4 months 24 days  
Debt instrument, description of variable rate London Interbank Offered Rate ("LIBOR")  
Debt covenant description in credit facility agreement At 31 March 2014, the Company was in compliance with all restrictive debt covenants contained in its credit facility agreements. Under the most restrictive of these covenants, the Company (i) must not exceed a maximum of net debt to earnings before interest, tax, depreciation and amortisation, excluding all income, expense and other profit and loss statement impacts of AICF, Amaba, Amaca, ABN 60 and Marlew Mining Pty Limited and excluding assets, liabilities and other balance sheet items of the AICF, Amaba, Amaca, ABN 60 and Marlew Mining Pty Limited, (ii) must meet or exceed a minimum ratio of earnings before interest and taxes to net interest charges, excluding all income, expense and other profit and loss statement impacts of AICF, Amaba, Amaca, ABN 60 and Marlew Mining Pty Limited, and (iii) must ensure that no more than 35% of Free Cash Flow (as defined in the AFFA), in any given financial year (“Annual Cash Flow Cap”) is contributed to AICF on the payment dates under the AFFA in the next following financial year. The Annual Cash Flow Cap does not apply to payments of interest, if any, to AICF and is consistent with contractual obligations of the Performing Subsidiary and the Company under the AFFA.  
Maximum percentage of Free Cash Flow contributed to AICF 35.00%  
Term facilities 355,000,000  
Term Facility Maturity April 2017 [Member]
   
Long Term Debt And Equity Financings [Line Items]    
Term facilities 75,000,000  
Subsequent Event [Member]
   
Long Term Debt And Equity Financings [Line Items]    
Term facilities 505,000,000  
Subsequent Event [Member] | Additional Term Facilities [Member]
   
Long Term Debt And Equity Financings [Line Items]    
Term facilities 150,000,000  
Subsequent Event [Member] | Term Facility Maturity April 2017 [Member]
   
Long Term Debt And Equity Financings [Line Items]    
Term facilities 25,000,000  
Term facilities, maturity period 2017-04  
Subsequent Event [Member] | Term Facility Maturity April 2019 [Member]
   
Long Term Debt And Equity Financings [Line Items]    
Term facilities 50,000,000  
Term facilities, maturity period 2019-04  
Subsequent Event [Member] | Term Facility Maturity May 2019 [Member]
   
Long Term Debt And Equity Financings [Line Items]    
Term facilities $ 75,000,000  
Term facilities, maturity period 2019-05