Fair Value Measurements - Nonrecurring Fair Value Measurements (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for impairment	$ 2,279	$ 11,177	$ 2,625	$ 11,177	$ 12,298
Nonrecurring Fair Value Measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment property	2,500		2,500		16,944
Provision for impairment			2,279
Nonrecurring Fair Value Measurements | Fair value, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment property					11,644
Nonrecurring Fair Value Measurements | Fair Value, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment property	$ 2,500		$ 2,500		$ 5,300
Weighted average | Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Input for measuring investment property					0.0689