Investment Securities (Details 5) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Hedge and private equity funds included in other long-term investments
Other long-term investments
Largest single fund investment	$ 34.3
Other long-term investments	283.5	315.5
Unfunded Commitments	83.8	88.7
Hedge funds
Other long-term investments
Number of limited partnership and limited liability corporation investments	17
Other long-term investments	139.1	155.7
Distributions outstanding	3.6
Redemption requests	2.2
Hedge funds | Monthly
Other long-term investments
Other long-term investments	5.7
Hedge funds | Monthly | 120+ days notice
Other long-term investments
Other long-term investments	5.7
Hedge funds | Quarterly
Other long-term investments
Other long-term investments	80.7
Hedge funds | Quarterly | 30-59 days notice
Other long-term investments
Other long-term investments	27.7
Hedge funds | Quarterly | 60-89 days notice
Other long-term investments
Other long-term investments	32.9
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	20.4
Hedge funds | Semi-annual | 60-89 days notice
Other long-term investments
Other long-term investments	5.5
Hedge funds | Semi-annual | 120+ days notice
Other long-term investments
Other long-term investments	14.9
Hedge funds | Annual
Other long-term investments
Other long-term investments	32.3
Hedge funds | Annual | 30-59 days notice
Other long-term investments
Other long-term investments	23.7
Hedge funds | Annual | 90-119 days notice
Other long-term investments
Other long-term investments	7.7
Hedge funds | Annual | 120+ days notice
Other long-term investments
Other long-term investments	0.9
Hedge funds | 30-59 days notice
Other long-term investments
Other long-term investments	51.4
Hedge funds | 60-89 days notice
Other long-term investments
Other long-term investments	38.4
Hedge funds | 90-119 days notice
Other long-term investments
Other long-term investments	27.8
Hedge funds | 120+ days notice
Other long-term investments
Other long-term investments	21.5
Long/short equity
Other long-term investments
Other long-term investments	51.1	50.4
Long/short credit & distressed
Other long-term investments
Other long-term investments	35.3	34.1
Long diversified strategies
Other long-term investments
Other long-term investments	23.8	24.0
Long/short equity REIT
Other long-term investments
Other long-term investments	14.9	25.2
Long/short equity activist
Other long-term investments
Other long-term investments	13.1	16.9
Long bank loan
Other long-term investments
Other long-term investments	0.9	5.1
Private equity funds
Other long-term investments
Number of limited partnership and limited liability corporation investments	33
Other long-term investments	144.4	159.8
Unfunded Commitments	83.8	88.7
Private equity funds | 1-3 years
Other long-term investments
Other long-term investments	50.8
Private equity funds | 5-10 years
Other long-term investments
Other long-term investments	79.5
Private equity funds | >10 years
Other long-term investments
Other long-term investments	14.1
Distressed residential real estate
Other long-term investments
Other long-term investments	34.3	49.2
Energy infrastructure and services
Other long-term investments
Other long-term investments	27.5	24.2
Unfunded Commitments	9.9	10.8
Multi-sector
Other long-term investments
Other long-term investments	26.8	26.0
Unfunded Commitments	9.1	10.6
Manufacturing/Industrial
Other long-term investments
Other long-term investments	14.1	17.9
Private equity secondaries
Other long-term investments
Other long-term investments	11.2	10.4
Unfunded Commitments	4.0	4.4
Real estate
Other long-term investments
Other long-term investments	9.8	9.1
Unfunded Commitments	4.2	4.6
International multi-sector, Europe
Other long-term investments
Other long-term investments	8.3	10.5
Unfunded Commitments	5.1	5.3
International multi-sector, Asia
Other long-term investments
Other long-term investments	3.8	4.9
Unfunded Commitments	2.7	2.7
Insurance
Other long-term investments
Other long-term investments	3.6	3.9
Unfunded Commitments	41.3	41.3
Venture capital fund
Other long-term investments
Other long-term investments	2.6	2.2
Unfunded Commitments	0.5	1.0
Healthcare
Other long-term investments
Other long-term investments	2.4	1.5
Unfunded Commitments	$ 7.0	$ 8.0