Investment Securities (Details 5) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Hedge and private equity funds included in other long-term investments
Other long-term investments
Largest single fund investment	$ 31.4
Other long-term investments	277.6	315.5
Unfunded Commitments	81.6	88.7
Hedge funds
Other long-term investments
Number of limited partnership and limited liability corporation investments	17
Other long-term investments	130.2	155.7
Distributions outstanding	3.2
Redemption requests	2.0
Hedge funds | Monthly
Other long-term investments
Other long-term investments	6.0
Hedge funds | Monthly | 120+ days notice
Other long-term investments
Other long-term investments	6.0
Hedge funds | Quarterly
Other long-term investments
Other long-term investments	75.4
Hedge funds | Quarterly | 30-59 days notice
Other long-term investments
Other long-term investments	26.1
Hedge funds | Quarterly | 60-89 days notice
Other long-term investments
Other long-term investments	29.7
Hedge funds | Quarterly | 90-119 days notice
Other long-term investments
Other long-term investments	19.6
Hedge funds | Semi-annual
Other long-term investments
Other long-term investments	19.8
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	14.7
Hedge funds | Annual
Other long-term investments
Other long-term investments	29.0
Hedge funds | Annual | 30-59 days notice
Other long-term investments
Other long-term investments	21.9
Hedge funds | Annual | 90-119 days notice
Other long-term investments
Other long-term investments	6.6
Hedge funds | Annual | 120+ days notice
Other long-term investments
Other long-term investments	0.5
Hedge funds | 30-59 days notice
Other long-term investments
Other long-term investments	48.0
Hedge funds | 60-89 days notice
Other long-term investments
Other long-term investments	34.8
Hedge funds | 90-119 days notice
Other long-term investments
Other long-term investments	26.2
Hedge funds | 120+ days notice
Other long-term investments
Other long-term investments	21.2
Long/short equity
Other long-term investments
Other long-term investments	49.0	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	22.0	24.0
Long/short equity REIT
Other long-term investments
Other long-term investments	14.7	25.2
Long/short equity activist
Other long-term investments
Other long-term investments	11.7	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 limited partnership and limited liability corporation investments	33
Other long-term investments	147.4	159.8
Unfunded Commitments	81.6	88.7
Private equity funds | 1-3 years
Other long-term investments
Other long-term investments	47.3
Private equity funds | 5-10 years
Other long-term investments
Other long-term investments	83.1
Private equity funds | >10 years
Other long-term investments
Other long-term investments	17.0
Distressed residential real estate
Other long-term investments
Other long-term investments	31.4	49.2
Energy infrastructure and services
Other long-term investments
Other long-term investments	29.5	24.2
Unfunded Commitments	9.9	10.8
Multi-sector
Other long-term investments
Other long-term investments	28.0	26.0
Unfunded Commitments	8.2	10.6
Manufacturing/Industrial
Other long-term investments
Other long-term investments	17.0	17.9
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	10.2	9.1
Unfunded Commitments	3.3	4.6
International multi-sector, Europe
Other long-term investments
Other long-term investments	8.0	10.5
Unfunded Commitments	4.7	5.3
International multi-sector, Asia
Other long-term investments
Other long-term investments	3.6	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	2.5	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