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Intangible Assets Narrative (Details) - Intangible Assets - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]        
Amortization of intangible assets $ 28.7 $ 25.8 $ 81.0 $ 73.3
Amortization of direct lease acquisition costs $ 13.6 $ 11.9 $ 36.9 $ 31.7
Direct lease acquisition costs | Minimum        
Finite-Lived Intangible Assets [Line Items]        
Intangible asset, useful life     28 days  
Direct lease acquisition costs | Maximum        
Finite-Lived Intangible Assets [Line Items]        
Intangible asset, useful life     1 year