Segment Reporting - Reconciliations Income Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 492,701	$ 384,293
Expenses:
Cost of revenues (exclusive of items shown separately below)	(173,277)	(133,784)
Selling, general and administrative	(71,037)	(49,714)
Investment income and others, net	44	(502)
EBITDA from discontinued operations	14,671	16,044
EBITDA	263,102	216,337
Depreciation and amortization of fixed assets	(31,887)	(19,388)
Amortization of intangible assets	(23,871)	(7,455)
Operating income	192,629	173,952
Interest expense	(32,032)	(18,262)
Income from continuing operations before income taxes	160,641	155,188
Operating Segments | Decision Analytics
Segment Reporting Information [Line Items]
Revenues	312,945	213,351
Expenses:
Cost of revenues (exclusive of items shown separately below)	(121,589)	(82,812)
Selling, general and administrative	(52,384)	(30,645)
Investment income and others, net	112	(569)
EBITDA from discontinued operations	14,671	16,044
EBITDA	153,755	115,369
Depreciation and amortization of fixed assets	(24,901)	(13,426)
Amortization of intangible assets	(23,783)	(7,367)
Operating income	90,288	79,101
Operating Segments | Risk Assessment
Segment Reporting Information [Line Items]
Revenues	179,756	170,942
Expenses:
Cost of revenues (exclusive of items shown separately below)	(51,688)	(50,972)
Selling, general and administrative	(18,653)	(19,069)
Investment income and others, net	(68)	67
EBITDA from discontinued operations	0	0
EBITDA	109,347	100,968
Depreciation and amortization of fixed assets	(6,986)	(5,962)
Amortization of intangible assets	(88)	(88)
Operating income	$ 102,341	$ 94,851