Transactions With Related Parties - Our Manager (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Related Party Transaction [Line Items]
Non-cash compensation expense	$ 7,303	$ 7,962	$ 14,268	$ 16,074
Common stock, shares outstanding (in shares)	171,593,590		171,593,590		172,792,094
Restricted Class A Common Stock
Related Party Transaction [Line Items]
Number of shares of restricted class A common stock outstanding (in shares)	1,933,440		1,933,440		2,142,759
Restricted shares, vesting period (in years)			3 years
Related Party
Related Party Transaction [Line Items]
Common stock, shares outstanding (in shares)	13,256,488		13,256,488
Percentage of stock	7.70%		7.70%
Subsidiary of Common Parent
Related Party Transaction [Line Items]
Common stock, shares outstanding (in shares)	8,234,581		8,234,581
Percentage of stock	4.80%		4.80%
Director | Deferred Stock Units
Related Party Transaction [Line Items]
Number of shares of restricted class A common stock outstanding (in shares)	323,877		323,877
BXMT Advisors Limited Liability Company and Affiliates | Related Party
Related Party Transaction [Line Items]
Management fee payable	$ 17,000		$ 17,000		$ 18,500
Manager | Related Party
Related Party Transaction [Line Items]
Renewal term (in years)			1 year
Management fees paid to manager	17,200	18,900	$ 35,800	45,300
Expenses	$ 156	829	$ 420	1,100
Manager | Related Party | Restricted Class A Common Stock
Related Party Transaction [Line Items]
Number of shares of restricted class A common stock outstanding (in shares)	992,441		992,441
Aggregate grant fair value			$ 20,700
Restricted shares, vesting period (in years)			3 years
Non-cash compensation expense	$ 3,600	$ 4,200	$ 7,200	$ 8,500