Segment Reporting - Reconciliations Income Before Income Taxes (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	May. 19, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenues		$ 497,650	$ 423,554	$ 957,047	$ 833,197
Expenses:
Cost of revenues (exclusive of items shown separately below)		(195,196)	(172,470)	(379,412)	(342,143)
Selling, general and administrative		(91,292)	(57,074)	(149,598)	(114,208)
Investment income and others, net		221	(200)	759	(209)
Gain on derivative instruments	$ (85,187)	(85,187)	0	(85,187)	0
EBITDA		296,128	194,210	512,465	432,643
Depreciation and amortization of fixed assets		(28,628)	(20,723)	(53,070)	(40,504)
Amortization of intangible assets		(28,812)	(14,221)	(42,953)	(28,433)
Gain on derivative instruments				0	(55,588)
Operating income		153,722	159,066	332,014	307,909
Operating Segments | Decision Analytics
Segment Reporting Information [Line Items]
Revenues		325,920	261,602	614,375	508,932
Expenses:
Cost of revenues (exclusive of items shown separately below)		(144,782)	(120,023)	(278,026)	(239,782)
Selling, general and administrative		(71,398)	(38,625)	(110,635)	(76,676)
Investment income and others, net		342	0	947	0
Gain on derivative instruments		(85,187)	0	(85,187)	0
EBITDA		194,585	102,954	309,954	248,062
Depreciation and amortization of fixed assets		(22,277)	(15,098)	(40,757)	(31,129)
Amortization of intangible assets		(28,723)	(14,132)	(42,776)	(28,256)
Gain on derivative instruments				0	(55,588)
Operating income		58,740	73,724	142,181	133,089
Operating Segments | Risk Assessment
Segment Reporting Information [Line Items]
Revenues		171,730	161,952	342,672	324,265
Expenses:
Cost of revenues (exclusive of items shown separately below)		(50,414)	(52,447)	(101,386)	(102,361)
Selling, general and administrative		(19,894)	(18,449)	(38,963)	(37,532)
Investment income and others, net		(121)	(200)	(188)	(209)
Gain on derivative instruments		0	0	0	0
EBITDA		101,543	91,256	202,511	184,581
Depreciation and amortization of fixed assets		(6,351)	(5,625)	(12,313)	(9,375)
Amortization of intangible assets		(89)	(89)	(177)	(177)
Gain on derivative instruments				0	0
Operating income		$ 94,982	$ 85,342	$ 189,833	$ 174,820