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Property and Equipment - Additional Disclosures (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Property, Plant and Equipment [Abstract]        
Depreciation expense $ 1.6 $ 1.9 $ 5.0 $ 5.9