Property and Equipment, Net (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property Plant And Equipment [Line Items]
Office and computer equipment (3 - 20 year estimated useful life)	$ 129.7	$ 119.7
Office furniture and fixtures (5 - 10 year estimated useful life)	40.6	40.3
Internal-use computer software (3 - 5 year estimated useful life)	284.9	263.9
Leasehold improvements (3 - 20 year estimated useful life)	199.2	197.5
Total property and equipment, at cost	654.4	621.4
Property and equipment, accumulated depreciation	375.7	314.3
Total property and equipment, net	$ 278.7	$ 307.1