Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Additional Information (Detail)

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Commitments and Contingencies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
Dec. 31, 2011
Data Processing, Outsourcing Services And Other Agreements | Minimum
    
Commitments and Contingencies Disclosure [Line Items]    
Service agreements expiration year 2012  
Estimated aggregate contractual obligation   $ 70
Data Processing, Outsourcing Services And Other Agreements | Maximum
    
Commitments and Contingencies Disclosure [Line Items]    
Service agreements expiration year 2018  
Expected future year's minimum contractual obligation   30
Agreement With Computer Sciences Corporation
    
Commitments and Contingencies Disclosure [Line Items]    
Service agreements expiration date Jul. 31, 2018  
Agreement renewable period 10 years  
Option to buy CSC credit reporting business exercise expected payment period The option exercise price will be determined by a third-party appraisal process and would be due in cash within 180 days after the exercise of the option.  
Agreement With Computer Sciences Corporation | Open Option Contracts
    
Commitments and Contingencies Disclosure [Line Items]    
CSC option to sell its credit reporting business, option expiration year Aug. 01, 2013  
Agreement With Computer Sciences Corporation | Minimum
    
Commitments and Contingencies Disclosure [Line Items]    
Estimated option exercise price   650
Agreement With Computer Sciences Corporation | Maximum
    
Commitments and Contingencies Disclosure [Line Items]    
Estimated option exercise price   $ 750
Guarantees
    
Commitments and Contingencies Disclosure [Line Items]    
Performance bonds and standby letters of credit remaining maturity date One year or less