Fair Value Measurements - Narrative (Details) - Property
6 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impairment of lease, expiration period (or less) 60 days  
Number of long-lived assets held and used accounted for at fair value 7 8
Number of long-lived assets held for sale accounted for fair value 1 1
Fair Value Estimated Using Ground Lease    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Number of long-lived assets held and used accounted for at fair value   3
Fair Value Estimated Using Comparable Properties    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Number of held and used property accounted for at fair value 4  
Fair Value Estimated Using Listing Price or Broker Opinion of Value    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Number of held and used property accounted for at fair value 3 5