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Summary of Significant Accounting Policies - Derivative Instruments (Details) - Interest Rate Swap
$ in Millions
6 Months Ended
Mar. 07, 2017
USD ($)
Jun. 30, 2017
USD ($)
instruments
Derivative [Line Items]    
Derivative, net hedge ineffectiveness gain (loss) $ (0.8)  
Cash Flow Hedging    
Derivative [Line Items]    
Outstanding interest rate swap contracts designated as cash flow hedges | instruments   5,000
Derivative, net hedge ineffectiveness gain (loss)   $ (0.2)