Fair Value Of Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Transfers of financial assets from level 2 to level 1	$ 10.6	$ 72.0
Fair Value Level One To Level Two Transfers Amount	27.2	32.6
General and limited partnership interests in investment partnerships	56.2	56.2		21.5
Direct investments in private equity companies held by private equity funds	10.8	10.8		13.5
Commitments Investments In Affiliated And Unaffiliated Partnerships	12.6	12.6		3.0
Stated interest rate			6.70%
KBW [Member]
Trading securities owned and investments purchased as part of KBW, Inc. acquisition		54.1
Amount sold during period		$ 6.3