Commitments, Contingencies And Guarantees (Commitments And Contingencies) (Details) $ in Millions	Sep. 30, 2015 USD ($)
Commitments And Guarantee Obligations [Line Items]
2015	$ 3,201.4
2016	2,016.8
2017 and 2018	1,117.7
2019 and 2020	107.1
2021 and Later	269.4
Maximum Payout	6,712.4
Equity Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	11.4
2016	107.7
2017 and 2018	67.0
2019 and 2020	48.8
2021 and Later	232.4
Maximum Payout	467.3
Loan Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	5.0
2016	356.0
2017 and 2018	450.3
2019 and 2020	52.3
2021 and Later	0.0
Maximum Payout	863.6
Mortgage-Related And Other Purchase Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	472.4
2016	1,553.1
2017 and 2018	576.4
2019 and 2020	0.0
2021 and Later	0.0
Maximum Payout	2,601.9
Forward Starting Reverse Repos And Repos [Member]
Commitments And Guarantee Obligations [Line Items]
2015	2,712.6
2016	0.0
2017 and 2018	0.0
2019 and 2020	0.0
2021 and Later	0.0
Maximum Payout	2,712.6
Other Unfunded Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	0.0
2016	0.0
2017 and 2018	24.0
2019 and 2020	6.0
2021 and Later	37.0
Maximum Payout	$ 67.0