Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 unit D	Dec. 31, 2010
Cash and Cash Equivalents
Maximum term of maturities upon acquisition to classify instruments as cash equivalents (in days)	90
Summary of property and equipment
Internal costs capitalized	$ 12.4	$ 14.0
Goodwill and Identifiable Intangible Assets
Number of reporting units for goodwill	2
Furniture and fixtures
Summary of property and equipment
Estimated useful lives, low end of range (in years)	3
Estimated useful lives, high end of range (in years)	10
Data processing equipment
Summary of property and equipment
Estimated useful lives, low end of range (in years)	5
Estimated useful lives, high end of range (in years)	10
Computer software
Summary of property and equipment
Estimated useful lives, low end of range (in years)	5
Estimated useful lives, high end of range (in years)	10
Equipment
Summary of property and equipment
Estimated useful lives, low end of range (in years)	3
Estimated useful lives, high end of range (in years)	26
Buildings
Summary of property and equipment
Estimated useful lives, low end of range (in years)	10
Estimated useful lives, high end of range (in years)	30
Leasehold improvements
Summary of property and equipment
Estimated useful lives, low end of range (in years)	1
Estimated useful lives, high end of range (in years)	15