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Summary of Significant Accounting Policies - Summary of Cash and Cash Equivalents and Grantor Trust by Investment Type (Details) - USD ($)
$ in Millions
Dec. 31, 2016
Dec. 31, 2015
Nov. 30, 2015
Nov. 30, 2014
Nov. 30, 2013
Cash and Cash Equivalents [Line Items]          
Cash and cash equivalents $ 410.3 $ 208.5 $ 211.1 $ 265.9 $ 197.6
Grantor trust (included as a component of other current and noncurrent assets) 8.0        
Total investment 418.3        
Cash and cash equivalents          
Cash and Cash Equivalents [Line Items]          
Cash and cash equivalents 89.8        
Grantor trust (included as a component of other current and noncurrent assets) 0.0        
Total investment 89.8        
Money Market Funds [Member]          
Cash and Cash Equivalents [Line Items]          
Cash and cash equivalents 320.5        
Grantor trust (included as a component of other current and noncurrent assets) 8.0        
Total investment $ 328.5