v2.4.0.6
Provision for Income Taxes - Expiration of Tax Credit Carryforwards (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Income Tax Disclosure [Line Items]  
Tax credit carryforwards $ 92
2013 Tax loss carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards   
2014 Tax Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards   
2015 Tax Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards   
2016 Tax Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards   
2017 Tax Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards   
2018-2022 Tax Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards   
Later Tax Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards 10
Unlimited Tax Credit Loss Carryforwards [Member]
  
Income Tax Disclosure [Line Items]  
Tax credit carryforwards $ 82