Fair Value Of Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Transfers of financial assets from level 2 to level 1	$ 56.3
Fair Value Level One To Level Two Transfers Amount	0.7
General and limited partnership interests in investment partnerships	57.7
Direct investments in private equity companies held by private equity funds	13.5
Commitments Investments In Affiliated And Unaffiliated Partnerships	13.8	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	$ 0.9