Investment Securities (Restrictions on Redemption Frequency and Advance Notice Requirements) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Investment securities
Distributions from inactive hedge funds	$ 3.3
Hedge funds
Investment securities
Other long-term investments	114.6
Investments entities that calculate net asset value per share redemption request	1.9
Monthly | Hedge funds
Investment securities
Other long-term investments	6.7
Quarterly | Hedge funds
Investment securities
Other long-term investments	76.3
Semi-annual | Hedge funds
Investment securities
Other long-term investments	21.8
Annual | Hedge funds
Investment securities
Other long-term investments	9.8
30-59 days notice | Hedge funds
Investment securities
Other long-term investments	30.1
30-59 days notice | Monthly | Hedge funds
Investment securities
Other long-term investments	0
30-59 days notice | Quarterly | Hedge funds
Investment securities
Other long-term investments	28.4
30-59 days notice | Semi-annual | Hedge funds
Investment securities
Other long-term investments	0
30-59 days notice | Annual | Hedge funds
Investment securities
Other long-term investments	1.7
60-89 days notice | Hedge funds
Investment securities
Other long-term investments	51.1
60-89 days notice | Monthly | Hedge funds
Investment securities
Other long-term investments	0
60-89 days notice | Quarterly | Hedge funds
Investment securities
Other long-term investments	29.3
60-89 days notice | Semi-annual | Hedge funds
Investment securities
Other long-term investments	21.8
60-89 days notice | Annual | Hedge funds
Investment securities
Other long-term investments	0
90-119 days notice | Hedge funds
Investment securities
Other long-term investments	16.5
90-119 days notice | Monthly | Hedge funds
Investment securities
Other long-term investments	0
90-119 days notice | Quarterly | Hedge funds
Investment securities
Other long-term investments	8.7
90-119 days notice | Semi-annual | Hedge funds
Investment securities
Other long-term investments	0
90-119 days notice | Annual | Hedge funds
Investment securities
Other long-term investments	7.8
120 days notice | Hedge funds
Investment securities
Other long-term investments	16.9
120 days notice | Monthly | Hedge funds
Investment securities
Other long-term investments	6.7
120 days notice | Quarterly | Hedge funds
Investment securities
Other long-term investments	9.9
120 days notice | Semi-annual | Hedge funds
Investment securities
Other long-term investments	0
120 days notice | Annual | Hedge funds
Investment securities
Other long-term investments	$ 0.3