Commitments, Contingencies And Guarantees (Commitments And Contingencies) (Details) $ in Millions	Sep. 30, 2016 USD ($)
Commitments And Guarantee Obligations [Line Items]
2016	$ 1,103.0
2017	988.9
2018 and 2019	1,395.6
2020 and 2021	95.0
2022 and Later	255.8
Maximum Payout	3,838.3
Equity Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	32.9
2017	42.3
2018 and 2019	16.4
2020 and 2021	13.9
2022 and Later	223.5
Maximum Payout	329.0
Loan Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	0.0
2017	317.6
2018 and 2019	87.2
2020 and 2021	54.4
2022 and Later	0.0
Maximum Payout	459.2
Mortgage-Related And Other Purchase Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	838.0
2017	263.2
2018 and 2019	1,265.2
2020 and 2021	21.6
2022 and Later	0.0
Maximum Payout	2,388.0
Underwriting Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	0.0
2017	223.2
2018 and 2019	0.0
2020 and 2021	0.0
2022 and Later	0.0
Maximum Payout	223.2
Forward Starting Reverse Repos And Repos [Member]
Commitments And Guarantee Obligations [Line Items]
2016	166.3
2017	0.0
2018 and 2019	0.0
2020 and 2021	0.0
2022 and Later	0.0
Maximum Payout	166.3
Other Unfunded Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	65.8
2017	142.6
2018 and 2019	26.8
2020 and 2021	5.1
2022 and Later	32.3
Maximum Payout	$ 272.6