Acquisitions (Details) (January 1, 2012 Thompson Insurance Enterprises, LLC [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Y
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Total consideration	$ 108.5
Cash consideration	100.5
Goodwill recognized	26.1
Other intangible assets recognized	81.2
Customer Relationships [Member]
Business Acquisition [Line Items]
Other intangible assets recognized	68.5
Weighted average amortization period, years	23
Trade Names [Member]
Business Acquisition [Line Items]
Other intangible assets recognized	11.5
Weighted average amortization period, years	10
Unpatented Technology [Member]
Business Acquisition [Line Items]
Other intangible assets recognized	$ 1.0
Weighted average amortization period, years	3