Fair Value Disclosure (Details) $ in Millions		12 Months Ended
		Dec. 31, 2017 USD ($) Instrument	Dec. 31, 2016 USD ($) Instrument	Dec. 31, 2015 USD ($)	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		$ (2.7)
Derivative, Net Liability Position, Aggregate Fair Value		32.4
Derivative Asset, Notional Amount		550.0	$ 550.0
Asset Impairment Charges		8.6	38.5	$ 33.9
Liabilities
Derivative, Notional Amount		285.6	412.1
Cash Flow Hedge Pre Tax Gain Loss to be Reclassified within Twelve Months		(4.3)
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Assets
Interest rate derivatives	[1]		2.9
Foreign Currency Cash Flow Hedge Asset at Fair Value	[2]	1.2	12.2
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	[2]		1.3
Liabilities
Interest rate derivatives	[1]	4.7	0.1
Foreign Currency Fair Value Hedge Liability at Fair Value	[2]	27.7
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member]
Liabilities
Foreign exchange rate derivatives	[2]	(6.9)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Assets
Interest rate derivatives	[1]		2.9
Foreign Currency Cash Flow Hedge Asset at Fair Value	[2]	1.2
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	[2]		1.3
Liabilities
Interest rate derivatives	[1]	4.7	$ 0.1
Foreign Currency Fair Value Hedge Liability at Fair Value	[2]	$ 27.7
Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Number of Instruments Held | Instrument		5	9
Other Nonoperating Income (Expense) [Member] | Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effective portion reclassified from accumulated other comprehensive loss		$ 38.9	$ (11.9)	(6.9)
Other Expense [Member] | Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net		8.0	(2.6)	(6.1)
Other Expense [Member] | Aae Cargo Ag [Member] | Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net				5.1
Cardinal Marine [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent					50.00%
Asset Impairment Charges				19.0
Portfolio Management [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges		3.7	6.7	31.0
Portfolio Management [Member] | Cardinal Marine [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges				19.0
Changes Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges		$ 8.6	2.0	3.1
Nordic Vessels [Member] | Changes Measurement [Member] | Portfolio Management [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges			$ 6.7	$ 30.8

[1] (1) Designated as hedges

[2] (2) Not designated as hedges