Acquisitions - Additional Information (Detail) - USD ($) $ in Millions			5 Months Ended	12 Months Ended
	Aug. 10, 2017	Mar. 01, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2016	May 21, 2015
Business Acquisition [Line Items]
Acquisition-Related Expenses				$ 22.5
Amortization expense				61.4	$ 34.2	$ 31.9
Tax Asset Resulting from Change in Non US Tax Rate under Tax Act			$ 57.9	57.9
Gilliland Gold Young (GGY) [Member]
Business Acquisition [Line Items]
Business acquisition interests acquired		100.00%
Acquired cash included in current assets		$ 7.5
Account receivables gross included in current assets		2.9
Amount related to transaction cost		0.9				$ 0.6	$ 0.3
Cash paid for business acquisition		$ 83.4
Equilibrium [Member]
Business Acquisition [Line Items]
Business acquisition interests acquired								100.00%
Bureau van Dijk (BvD) [Member]
Business Acquisition [Line Items]
Business acquisition interests acquired	100.00%
Acquired cash included in current assets	$ 36.0
Account receivables gross included in current assets	88.0
Amount related to transaction cost	8.6
Cash paid for business acquisition	3,542.0
Revenue since Acquisition Date, Actual			92.4
Net income from continuing operations since Acquisition Date, Actual			63.7
Integration Costs			13.9
Reduction in Revenue included in net income			36.0	1.0	$ 58.0
Reduction in Deferred Revenue to establish the fair value			53.0
Acquisition-Related Expenses			22.5
Allowance for Uncollectible Accounts	3.7
Amortization expense			28.0
Remaining Reduction in Deferred Revenue to establish the fair value			17.0	17.0
Acquired Deferred Revenue	$ 154.0
Tax Asset Resulting from Change in Non US Tax Rate under Tax Act			$ 57.9	$ 57.9