Financial Instruments and Risk Management (Schedule of Available-for-sale Securities Reconciliation) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 59.4	$ 55.6
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	24.6	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(0.3)	(1.6)
Fair Value	83.7	54.0
Debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31.4	28.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0.0	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	(0.3)
Fair Value	31.4	28.0
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28.0	27.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	24.6	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(0.3)	(1.3)
Fair Value	$ 52.3	$ 26.0