Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 unit item	Dec. 31, 2011
Summary of Significant Accounting Policies
Number of operating business segments	1
Summary of property and equipment
Internal costs capitalized	$ 9.6	$ 12.5
Goodwill and Identifiable Intangible Assets
Number of reporting units for goodwill	2
Furniture and fixtures | Minimum
Summary of property and equipment
Estimated useful lives	3 years
Furniture and fixtures | Maximum
Summary of property and equipment
Estimated useful lives	10 years
Data processing equipment | Minimum
Summary of property and equipment
Estimated useful lives	2 years
Data processing equipment | Maximum
Summary of property and equipment
Estimated useful lives	5 years
Computer software | Minimum
Summary of property and equipment
Estimated useful lives	1 year
Computer software | Maximum
Summary of property and equipment
Estimated useful lives	10 years
Equipment | Minimum
Summary of property and equipment
Estimated useful lives	3 years
Equipment | Maximum
Summary of property and equipment
Estimated useful lives	26 years
Buildings | Minimum
Summary of property and equipment
Estimated useful lives	10 years
Buildings | Maximum
Summary of property and equipment
Estimated useful lives	30 years
Leasehold improvements | Minimum
Summary of property and equipment
Estimated useful lives	1 year
Leasehold improvements | Maximum
Summary of property and equipment
Estimated useful lives	15 years