Fair Value Measures Fair Value Measures - Items Measured at Fair Value on a Non-Recurring Basis (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
Impairment charges	$ 11,988	$ 6,036
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of real estate assets deemed to be impaired	61,400	14,200
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of real estate assets deemed to be impaired	$ 49,400	$ 8,200
Measurement Input, Discount Rate [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement Input	0.080
Measurement Input, Cap Rate [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement Input	0.075