Derivative Financial Instruments Schedule of Notional Amounts (Details) $ in Millions	Sep. 30, 2017 USD ($)
Derivative [Line Items]
Total	$ 6,550.5
Swaps
Derivative [Line Items]
Total	272.8
Futures, forwards and spot
Derivative [Line Items]
Total	3,174.1
Written options
Derivative [Line Items]
Total	1,338.6
Purchased options
Derivative [Line Items]
Total	$ 1,765.0