Useful Life of Other Purchased Intangible Assets (Detail)	12 Months Ended
	Dec. 31, 2011 Year
Purchased data files
Finite-Lived Intangible Assets [Line Items]
Useful Life, Minimum	2
Useful Life, Maximum	15
Acquired software and technology
Finite-Lived Intangible Assets [Line Items]
Useful Life, Minimum	1
Useful Life, Maximum	10
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Useful Life, Minimum	1
Useful Life, Maximum	10
Proprietary database
Finite-Lived Intangible Assets [Line Items]
Useful Life, Minimum	6
Useful Life, Maximum	10
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful Life, Minimum	2
Useful Life, Maximum	25
Trade names
Finite-Lived Intangible Assets [Line Items]
Useful Life, Minimum	5
Useful Life, Maximum	15