Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 29, 2019	Jan. 01, 2019	Dec. 31, 2018
Significant Of Accounting Policies [Line Items]
Assets excluding BREIT OP	$ 3,600,000,000			$ 2,800,000,000
Liabilities excluding BREIT OP	$ 2,500,000,000			1,900,000,000
Ground leases discount rate	7.00%
Operating lease, ROU assets	$ 45,678,000
Operating lease, liabilities	31,483,000
Finance lease, ROU assets	62,130,000
Finance lease, liabilities	60,308,000			4,300,000
Account Standards Update 2016-02
Significant Of Accounting Policies [Line Items]
Ground leases discount rate			7.00%
Operating lease, ROU assets			$ 31,300,000
Operating lease, liabilities			31,300,000
Prepaid ground lease intangible asset reclassified as ROU operating asset			15,700,000
Finance lease, ROU assets		$ 56,000,000
Finance lease, liabilities		$ 56,000,000
Existing financing lease liability	4,300,000
Below-market ground lease intangible asset reclassified as ROU operating asset	4,500,000
Above-market ground lease intangible liability reclassified as ROU operating asset	4,600,000
Straight-line ground rent liability reclassified as ROU operating asset	1,200,000
Acquired financing ROU asset	$ 6,100,000
Lease, practical expedients package	true
Lease, practical expedient, use of hindsight	false
Impact to retained earnings as a result of ASU adoption			$ 0
Rental revenue previously classified as tenant reimbursement income	$ 9,000,000
Level 2 [Member]
Significant Of Accounting Policies [Line Items]
Investments in real estate-related securities	2,400,000,000			$ 2,300,000,000
Level 3 [Member]
Significant Of Accounting Policies [Line Items]
Mortgage notes, term loans, and revolving credit facilities, repurchase agreements, and affiliate line of credit	$ 17,600,000