XML 70 R68.htm IDEA: XBRL DOCUMENT v2.4.0.6
Commitments and Contingencies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
1 Months Ended 12 Months Ended
Jun. 30, 2010
Mar. 31, 2013
Contract
GeneratingPlant
Mar. 31, 2012
Mar. 31, 2011
Jan. 19, 2012
Jul. 31, 2010
Mar. 31, 2010
Commitments And Contingencies [Line Items]              
Contingent liabilities under outstanding letters of credit   $ 7.1          
Contingently liable for performance, current   13.6          
Notice of Deficiency received for taxes and penalties related to IRS audit 71.5            
Notice of Deficiency received for taxes and penalties including interest 97.9            
Taxes and penalties including interest deposited with IRS 75            
Total taxes and penalties including interest deposited with IRS           97.9  
Assessment of income tax             8.1
Assessment of penalties             1.9
Income tax interest accrued   1.9          
Number of agreements   2          
Legal award to mining companies         6.9    
Legal award to other parties         1.2    
Sale percentage of gypsum-grade recycled paperboard   90.00%          
Number of plants   3          
Percentage of expected natural gas usage   25.00%          
Operating leases Rental expense   $ 1.6 $ 1.7 $ 2.0      
Minimum [Member]
             
Commitments And Contingencies [Line Items]              
Sale percentage of gypsum-grade recycled paperboard   15.00%          
Maximum [Member]
             
Commitments And Contingencies [Line Items]              
Sale percentage of gypsum-grade recycled paperboard   20.00%