Financial Information by Segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenue	$ 779.2	$ 705.5	$ 756.0	$ 731.8	$ 754.2	$ 688.5	$ 640.8	$ 646.8	$ 2,972.5	$ 2,730.3	$ 2,280.7
Operating, SG&A									1,644.5	1,547.2	1,313.1
Adjusted Operating Income									1,328.0	1,183.1	967.6
Depreciation and amortization									93.4	93.5	79.2
Goodwill impairment charge					12.2				0	12.2	0
Operating income	311.9	291.5	350.8	280.4	260.2	269.7	278.5	269.0	1,234.6	1,077.4	888.4
MIS
Segment Reporting Information [Line Items]
Revenue									2,138.0	1,958.3	1,634.7
Operating, SG&A									1,022.6	967.6	832.3
Adjusted Operating Income									1,115.4	990.7	802.4
Depreciation and amortization									46.6	44.2	41.2
Goodwill impairment charge									0	0
Operating income									1,068.8	946.5	761.2
MA
Segment Reporting Information [Line Items]
Revenue									924.7	855.3	722.4
Operating, SG&A									712.1	662.9	557.2
Adjusted Operating Income									212.6	192.4	165.2
Depreciation and amortization									46.8	49.3	38.0
Goodwill impairment charge									0	12.2
Operating income									165.8	130.9	127.2
Eliminations
Segment Reporting Information [Line Items]
Revenue									(90.2)	(83.3)	(76.4)
Operating, SG&A									(90.2)	(83.3)	(76.4)
Adjusted Operating Income									0	0	0
Depreciation and amortization									0	0	0
Goodwill impairment charge										0
Operating income									$ 0	$ 0	$ 0