Commitments, Contingencies And Guarantees (Commitments And Contingencies) (Details) $ in Millions	Mar. 31, 2016 USD ($)
Commitments And Guarantee Obligations [Line Items]
2016	$ 1,502.1
2017	831.5
2018 and 2019	1,019.3
2020 and 2021	19.8
2022 and Later	283.5
Maximum Payout	3,656.2
Equity Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	22.8
2017	19.0
2018 and 2019	0.0
2020 and 2021	14.3
2022 and Later	248.5
Maximum Payout	304.6
Loan Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	2.5
2017	341.4
2018 and 2019	55.9
2020 and 2021	0.0
2022 and Later	0.0
Maximum Payout	399.8
Mortgage-Related And Other Purchase Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	1,352.2
2017	255.3
2018 and 2019	926.4
2020 and 2021	0.0
2022 and Later	0.0
Maximum Payout	2,533.9
Forward Starting Reverse Repos And Repos [Member]
Commitments And Guarantee Obligations [Line Items]
2016	77.1
2017	0.0
2018 and 2019	0.0
2020 and 2021	0.0
2022 and Later	0.0
Maximum Payout	77.1
Other Unfunded Commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2016	47.5
2017	215.8
2018 and 2019	37.0
2020 and 2021	5.5
2022 and Later	35.0
Maximum Payout	$ 340.8