Acquisition - Summary of Purchase Price Allocation (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Aug. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 4,183,981		$ 3,546,034
STP
Business Acquisition [Line Items]
Trade and other receivables		$ 238,997
Prepaid expenses and other		5,163
Deferred tax assets		2,353
Property and equipment		46,024
Other long term assets		1,029
Goodwill		621,741
Other intangible assets	642,012	642,012
Deferred tax liabilities		(4,905)
Liabilities assumed		(303,369)
Aggregate purchase prices		$ 1,249,045
Other
Business Acquisition [Line Items]
Trade and other receivables	27,810
Prepaid expenses and other	5,097
Deferred tax assets	146
Property and equipment	992
Goodwill	21,820
Other intangible assets	63,410
Other intangible assets	63,410
Liabilities assumed	(42,541)
Aggregate purchase prices	$ 76,734
2015 Acquisitions
Business Acquisition [Line Items]
Trade and other receivables			521
Prepaid expenses and other			996
Property and equipment			197
Goodwill			9,561
Other intangible assets			39,791
Other intangible assets			39,791
Deferred tax liabilities			(2,331)
Liabilities assumed			(2,437)
Aggregate purchase prices			$ 46,298