Segment Reporting - Operating Segment Revenue by Type of Service (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 498,296	$ 428,599	$ 990,997	$ 812,892
Operating Segments | Decision Analytics
Segment Reporting Information [Line Items]
Revenues	317,179	256,869	630,124	470,220
Operating Segments | Decision Analytics | Insurance
Segment Reporting Information [Line Items]
Revenues	175,476	165,276	347,021	319,009
Operating Segments | Decision Analytics | Financial services
Segment Reporting Information [Line Items]
Revenues	30,585	26,380	59,059	61,550
Operating Segments | Decision Analytics | Energy and specialized markets
Segment Reporting Information [Line Items]
Revenues	111,118	65,213	224,044	89,661
Operating Segments | Risk Assessment
Segment Reporting Information [Line Items]
Revenues	181,117	171,730	360,873	342,672
Operating Segments | Risk Assessment | Industry-standard insurance programs
Segment Reporting Information [Line Items]
Revenues	138,599	130,776	276,026	261,372
Operating Segments | Risk Assessment | Property-specific rating and underwriting information
Segment Reporting Information [Line Items]
Revenues	$ 42,518	$ 40,954	$ 84,847	$ 81,300