Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of assets pledged to secure a debt instrument.

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Financial Statements for Guarantors of the Senior Notes - Paragraph - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Restricted cash	$ 195.2	$ 178.2
Assets	9,543.2	9,125.3	$ 8,885.9
Non-US \| Combined Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Assets	317.3	349.4
Secured debt \| Combined Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net book value pledged as collateral	3,509.1	3,300.9
Capital lease obligations \| Combined Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net book value pledged as collateral	66.2	68.0
Reportable legal entities \| Combined Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Restricted cash	143.0	147.1
Assets	$ 5,489.3	$ 5,255.9