Investments in Unconsolidated Entities - Summarized Balance Sheet with Reconciliation To Equity Investment In Unconsolidated Entities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Total assets	$ 37,032,808		$ 33,039,823
Total liabilities	(21,800,839)		(22,404,026)
Total equity	15,204,028	$ 14,569,513	$ 10,614,648	$ 8,403,652	$ 6,376,375	$ 3,914,954
Investments in unconsolidated entities	814,134
BREIT MGP JV [Member]
Schedule Of Equity Method Investments [Line Items]
Investments in unconsolidated entities	814,134
BREIT MGP JV [Member] | Equity Method Investment [Member]
Schedule Of Equity Method Investments [Line Items]
Total assets	4,614,202
Total liabilities	(3,001,555)
Total equity	1,612,647
BREIT MGP JV [Member] | BREIT's Share [Member]
Schedule Of Equity Method Investments [Line Items]
Investments in unconsolidated entities	804,711
BREIT MGP JV [Member] | BREIT Outside Basis [Member]
Schedule Of Equity Method Investments [Line Items]
Investments in unconsolidated entities	9,423
BREIT MGP JV [Member] | MGM Growth Properties LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Investments in unconsolidated entities	$ 807,936