Fair Value Measures - Impairment Charges by Asset Class (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) property	Mar. 31, 2018 USD ($) property
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Properties impaired | property	24	12
Below-market lease liabilities, net	$ 0	$ (7)
Total impairment loss	11,988	6,036
Real Estate Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	$ 11,988	$ 6,043