Investment Securities (Other investments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments	$ 143.0		$ 139.6
Community Reinvestment Vehicle [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments	14.4		14.4
Long/short credit and distressed
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	8.3		8.1
Long bank loan
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0.1		0.1
Long/short equity
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	41.3		39.1
Long/short equity activist
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.2		2.1
Hedge funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments	51.9		49.4
Other investments at fair value	51.9		49.4
Distributions from inactive hedge funds	0.9
Redemption requests	2.2
Hedge funds | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	8.3
Hedge funds | Investment Redemption Notice Period over 120 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	5.6
Hedge funds | Investment Redemption Notice Period 90 to 119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	8.5
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	29.5
Hedge funds | Monthly
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	7.5
Hedge funds | Monthly | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds | Monthly | Investment Redemption Notice Period over 120 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	5.5
Hedge funds | Monthly | Investment Redemption Notice Period 90 to 119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds | Monthly | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.0
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	42.2
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	8.3
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | Investment Redemption Notice Period over 120 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | Investment Redemption Notice Period 90 to 119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	6.4
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	27.5
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.2
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | Investment Redemption Notice Period over 120 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0.1
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | Investment Redemption Notice Period 90 to 119 Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.1
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Insurance
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.4		2.3
Net asset value per share of unfunded commitments	0.1		0.1
Distressed residential real estate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0		0.2
Net asset value per share of unfunded commitments	0		0
Energy infrastructure and services
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	26.3		26.0
Net asset value per share of unfunded commitments	5.7		5.9
Healthcare
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	3.9		2.8
Net asset value per share of unfunded commitments	1.4		1.4
Multi-sector
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	14.9		14.5
Net asset value per share of unfunded commitments	2.5		2.5
Private equity secondaries
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	6.2		6.4
Net asset value per share of unfunded commitments	2.1		2.1
Real estate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	3.5		3.9
Net asset value per share of unfunded commitments	0.1		0.1
Private equity funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments	57.2		56.1
Other investments at fair value	57.2		56.1
Net asset value per share of unfunded commitments	11.9		12.1
Private equity funds | 1 - 3 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.4
Private equity funds | 3 - 5 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	19.3
Private equity funds | 5 - 10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	35.5
Private equity funds | >10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds and private equity funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	109.1	[1]	105.5	[1]
Net asset value per share of unfunded commitments	$ 11.9	[1]	$ 12.1	[1]

[1] Excluded from the above table as of March 31, 2014 and December 31, 2013 are other investments, which include an investment in a community reinvestment vehicle of $14.4 million for both periods and an investment in a tax advantaged federal affordable housing development fund of $19.3 million and $19.7 million, respectively. Additionally, other investments includes trust certificates issued upon dissolution of a private equity fund of $0.2 million as of March 31, 2014, with no such investment held as of December 31, 2013.