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Intangible Assets Narrative (Details) - Intangible Assets - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Finite-Lived Intangible Assets [Line Items]        
Amortization of intangible assets $ 27.6 $ 25.0 $ 52.3 $ 47.5
Amortization of direct lease acquisition costs $ 13.0 $ 11.1 $ 23.3 $ 19.8
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