Related Party Arrangements - Colony NorthStar Line of Credit (Narrative) (Details) - Line of Credit - Colony NorthStar, Inc. - USD ($)	6 Months Ended
Jun. 30, 2019	Nov. 30, 2017	Oct. 31, 2017
Related Party Transaction [Line Items]
Maximum borrowing capacity	$ 35,000,000	$ 35,000,000.0	$ 15,000,000.0
LIBOR
Related Party Transaction [Line Items]
Interest rate (percentage)	3.50%

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant