Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
apportionment_issue
Mar. 31, 2014
Income Taxes [Line Items]    
Effective income tax rate 32.40% 25.50%
Unrecognized tax benefits $ 10  
Unrecognized tax benefits that, if recognized, would impact the effective tax rate 7  
State apportionment issues expected to be resolve during the next 12 months 2  
Net cash payments (receipts) for income tax (refunds) 58 25
US Federal Tax Issue    
Income Taxes [Line Items]    
Change in unrecognized tax benefits, amount of unrecorded benefit 21  
State Apportionment Issues    
Income Taxes [Line Items]    
Change in unrecognized tax benefits, amount of unrecorded benefit $ 4