Investment Securities (Details 8) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Hedge and private equity funds included in other long-term investments
Other long-term investments
Largest single fund investment	$ 27.4	$ 49.2
Other long-term investments	254.2	315.5
Unfunded Commitments	81.5	88.7
Hedge funds
Other long-term investments
Number of investments	16
Other long-term investments	125.3	155.7
Distributions outstanding	3.3
Redemption requests	2.2
Hedge funds | 30-59 days notice
Other long-term investments
Other long-term investments	44.4
Hedge funds | 60-89 days notice
Other long-term investments
Other long-term investments	32.1
Hedge funds | 90-119 days notice
Other long-term investments
Other long-term investments	27.3
Hedge funds | 120+ days notice
Other long-term investments
Other long-term investments	21.5
Hedge funds | Monthly
Other long-term investments
Other long-term investments	6.5
Hedge funds | Monthly | 120+ days notice
Other long-term investments
Other long-term investments	6.5
Hedge funds | Quarterly
Other long-term investments
Other long-term investments	74.6
Hedge funds | Quarterly | 30-59 days notice
Other long-term investments
Other long-term investments	27.5
Hedge funds | Quarterly | 60-89 days notice
Other long-term investments
Other long-term investments	27.0
Hedge funds | Quarterly | 90-119 days notice
Other long-term investments
Other long-term investments	20.1
Hedge funds | Semi-annual
Other long-term investments
Other long-term investments	19.6
Hedge funds | Semi-annual | 60-89 days notice
Other long-term investments
Other long-term investments	5.1
Hedge funds | Semi-annual | 120+ days notice
Other long-term investments
Other long-term investments	14.5
Hedge funds | Annual
Other long-term investments
Other long-term investments	24.6
Hedge funds | Annual | 30-59 days notice
Other long-term investments
Other long-term investments	16.9
Hedge funds | Annual | 90-119 days notice
Other long-term investments
Other long-term investments	7.2
Hedge funds | Annual | 120+ days notice
Other long-term investments
Other long-term investments	0.5
Long/short equity
Other long-term investments
Other long-term investments	48.8	50.4
Long/short credit & distressed
Other long-term investments
Other long-term investments	32.3	34.1
Long diversified strategies
Other long-term investments
Other long-term investments	16.9	25.2
Long/short equity REIT
Other long-term investments
Other long-term investments	14.5	24.0
Long/short equity activist
Other long-term investments
Other long-term investments	12.3	16.9
Long bank loan
Other long-term investments
Other long-term investments	0.5	5.1
Private equity funds
Other long-term investments
Number of investments	32
Other long-term investments	128.9	159.8
Unfunded Commitments	81.5	88.7
Private equity funds | 1-3 years
Other long-term investments
Other long-term investments	42.9
Private equity funds | 5-10 years
Other long-term investments
Other long-term investments	79.8
Private equity funds | >10 years
Other long-term investments
Other long-term investments	6.2
Energy infrastructure and services
Other long-term investments
Other long-term investments	28.0	24.2
Unfunded Commitments	9.9	10.8
Distressed residential real estate
Other long-term investments
Other long-term investments	27.4	49.2
Multi-sector
Other long-term investments
Other long-term investments	26.9	26.0
Unfunded Commitments	8.2	10.6
Private equity secondaries
Other long-term investments
Other long-term investments	11.3	10.4
Unfunded Commitments	4.0	4.4
Real estate
Other long-term investments
Other long-term investments	9.5	9.1
Unfunded Commitments	3.3	4.6
International multi-sector, Europe
Other long-term investments
Other long-term investments	7.8	10.5
Unfunded Commitments	4.7	5.3
Manufacturing/Industrial
Other long-term investments
Other long-term investments	6.2	17.9
International multi-sector, Asia
Other long-term investments
Other long-term investments	3.6	4.9
Unfunded Commitments	2.6	2.7
Insurance
Other long-term investments
Other long-term investments	3.5	3.9
Unfunded Commitments	41.3	41.3
Venture capital fund
Other long-term investments
Other long-term investments	2.4	2.2
Unfunded Commitments	0.5	1.0
Healthcare
Other long-term investments
Other long-term investments	2.3	1.5
Unfunded Commitments	7.0	8.0
Federal affordable housing development fund
Other long-term investments
Unfunded Commitments	10.1
Investment in a tax advantaged federal affordable housing development fund included in other long-term investments	$ 21.8