Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Significant Of Accounting Policies [Line Items]
Assets excluding BREIT OP	$ 2,800,000	$ 947,900
Liabilities excluding BREIT OP	1,900,000	645,500
Subscriptions received in advance, common stock	$ 166,500	107,600
Percentage of taxable income distributed to stockholders	90.00%
Investments in real estate-related securities	$ 2,259,913	915,742
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member]
Significant Of Accounting Policies [Line Items]
Straight line ground rent liability			$ 1,200
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Above-market Lease [Member]
Significant Of Accounting Policies [Line Items]
Ground lease intangible liability			4,600
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Minimum [Member]
Significant Of Accounting Policies [Line Items]
ROU asset			25,000
Operating lease liability			25,000
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Maximum [Member]
Significant Of Accounting Policies [Line Items]
ROU asset			39,000
Operating lease liability			$ 39,000
Operating lease term			12 months
Level 2 [Member]
Significant Of Accounting Policies [Line Items]
Investments in real estate-related securities	2,300,000	900,000
Level 3 [Member]
Significant Of Accounting Policies [Line Items]
Mortgage notes, term loans, and revolving credit facilities, repurchase agreements, and affiliate line of credit	6,900
Hyatt Place Uc Davis [Member] | Other Assets [Member]
Significant Of Accounting Policies [Line Items]
Deferred tax assets	1,800	300
Hyatt Place Uc Davis [Member] | Other Income [Member]
Significant Of Accounting Policies [Line Items]
Tax benefit	$ 600	300
Class T Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.85%
Selling commissions and dealer manager fees (% of transaction price)	3.50%
Upfront selling commissions and dealer manager fees (% of transaction price)	3.00%
Selling commissions and upfront dealer manager fees (% of transaction price)	0.50%
Advisor stockholder servicing fee (% of NAV)	0.65%
Dealer stockholder servicing fee (% of NAV)	0.20%
Class T Shares [Member] | Maximum [Member]
Significant Of Accounting Policies [Line Items]
Selling commissions and dealer manager fees (% of transaction price)	3.50%
Class S Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.85%
Selling commissions and dealer manager fees (% of transaction price)	3.50%
Class S Shares [Member] | Maximum [Member]
Significant Of Accounting Policies [Line Items]
Selling commissions and dealer manager fees (% of transaction price)	3.50%
Class D Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.25%
Selling commissions and dealer manager fees (% of transaction price)	1.50%
Class D Shares [Member] | Maximum [Member]
Significant Of Accounting Policies [Line Items]
Selling commissions and dealer manager fees (% of transaction price)	1.50%
Class S Shares, Class D Shares and Class T Shares [Member]
Significant Of Accounting Policies [Line Items]
Stockholder servicing fees accrued	$ 238,500	102,100
Adviser [Member]
Significant Of Accounting Policies [Line Items]
Organizational and offering costs		$ 10,200
Period for reimbursement of advance expenses	60 months
Reimbursement of organization and offering costs	$ 2,000
Blackstone Advisory Partners L.P. [Member]
Significant Of Accounting Policies [Line Items]
Commission and fees, threshold percentage on gross proceeds from sale of share	8.75%
Blackstone Advisory Partners L.P. [Member] | Class T Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.85%
Blackstone Advisory Partners L.P. [Member] | Class S Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.85%
Blackstone Advisory Partners L.P. [Member] | Class D Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.25%
Blackstone Advisory Partners L.P. [Member] | Class I Shares [Member]
Significant Of Accounting Policies [Line Items]
Percentage of stockholder servicing fee on NAV per annum	0.00%