Segment Reporting - Operating Segment Revenue by Type of Service (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 409,643	$ 376,697
Operating Segments | Decision Analytics
Segment Reporting Information [Line Items]
Revenues	247,330	224,084
Operating Segments | Decision Analytics | Insurance
Segment Reporting Information [Line Items]
Revenues	141,430	126,549
Operating Segments | Decision Analytics | Financial services
Segment Reporting Information [Line Items]
Revenues	21,016	17,282
Operating Segments | Decision Analytics | Healthcare
Segment Reporting Information [Line Items]
Revenues	63,896	59,049
Operating Segments | Decision Analytics | Specialized markets
Segment Reporting Information [Line Items]
Revenues	20,988	21,204
Operating Segments | Risk Assessment
Segment Reporting Information [Line Items]
Revenues	162,313	152,613
Operating Segments | Risk Assessment | Industry-standard insurance programs
Segment Reporting Information [Line Items]
Revenues	123,817	116,450
Operating Segments | Risk Assessment | Property-specific rating and underwriting information
Segment Reporting Information [Line Items]
Revenues	$ 38,496	$ 36,163