Borrowings - Narrative (Details) - USD ($)			1 Months Ended		3 Months Ended		9 Months Ended
	Jul. 01, 2020	May 01, 2020	Apr. 30, 2020	Oct. 31, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Nov. 30, 2017
Line of Credit Facility [Line Items]
Forbearance period (days)		90 days
Principal amount of debt deferred					$ 1,300,000,000		$ 1,300,000,000
Forbearance repayment period (months)							12 months
Interest expense					16,459,000	$ 17,218,000	$ 49,591,000	$ 51,908,000
Mortgage notes payable, net
Line of Credit Facility [Line Items]
Principal Amount					1,441,218,000		1,441,218,000		$ 1,455,413,000
Rochester, NY | Mortgage notes payable, net
Line of Credit Facility [Line Items]
Maximum days of interest deferred	90 days
Maximum duration of principal payments to be deferred		120 days
Principal Amount					19,900,000		19,900,000
Colony NorthStar, Inc. | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 15,000,000.0	35,000,000.0		35,000,000.0			$ 35,000,000.0
Expiration term (in years)				1 year
Line of credit extension term (in months)				6 months
Proceeds drawn under line of credit			$ 35,000,000.0
Interest expense					$ 300,000		$ 600,000
LIBOR | Colony NorthStar, Inc. | Line of Credit
Line of Credit Facility [Line Items]
Interest rate (percentage)							3.50%