Revenues and Operating Earnings Based on Originating Location (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues	$ 803.2	$ 766.7	$ 768.1	$ 747.3	$ 654.7	$ 636.0	$ 608.9	$ 600.2	$ 3,085.3		$ 2,499.8		$ 1,984.2
Operating earnings (loss)									540.0	[1]	428.0	[1]	316.0	[1]
Domestic
Segment Reporting Information [Line Items]
Revenues									2,230.1		1,750.2		1,422.6
Operating earnings (loss)									334.2		246.9		181.3
Foreign
Segment Reporting Information [Line Items]
Revenues									855.2		749.6		561.6
Operating earnings (loss)									$ 205.8		$ 181.1		$ 134.7

[1] Operating earnings includes an allocation of corporate IT costs, employee benefits and general and administrative costs based on the proportion of each segment's systems users, number of employees and sales, respectively.