Derivative Instruments and Hedging Activities - Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2016	Jun. 30, 2015
Derivative assets:
Derivative asset, gross	$ 89.1	$ 60.1
Gross amounts offset in the balance sheet	(36.8)	(17.2)
Cash collateral received	(2.3)	0.0
Total derivative assets - net	50.0	42.9
Derivative liabilities:
Derivative liability, gross	(76.0)	(154.7)
Gross amounts offset in the balance sheet	36.8	17.2
Cash collateral pledged	0.0	2.2
Total derivative liabilities - net	(39.2)	(135.3)
Designated as Hedging Instrument
Derivative assets:
Derivative asset, gross	18.9	38.3
Derivative liabilities:
Derivative liability, gross	(4.6)	(2.1)
Designated as Hedging Instrument | Foreign currency contracts
Derivative assets:
Derivative asset, gross	18.6	29.1
Derivative liabilities:
Derivative liability, gross	(0.8)	(0.1)
Designated as Hedging Instrument | Cross-currency contracts
Derivative assets:
Derivative asset, gross	0.3	8.2
Designated as Hedging Instrument | Interest rate contracts
Derivative assets:
Derivative asset, gross	0.0	1.0
Derivative liabilities:
Derivative liability, gross	(3.8)	(2.0)
Derivatives Subject to PGC and DS Mechanisms | Commodity contracts
Derivative assets:
Derivative asset, gross	5.7	1.9
Derivative liabilities:
Derivative liability, gross	(0.6)	(4.8)
Derivatives Not Designated as Hedging Instruments | Commodity contracts
Derivative assets:
Derivative asset, gross	64.5	19.9
Derivative liabilities:
Derivative liability, gross	$ (70.8)	$ (147.8)