Subsequent Events - Additional Information (Detail) - USD ($) $ in Thousands		9 Months Ended
	Oct. 05, 2021	Sep. 30, 2021	Sep. 30, 2020
Proceeds from long term secured debt		$ 7,701,481	$ 2,317,616
Subsequent Event [Member] | Three Point Seven Five Senior Secured Notes due Two Thousand Twenty Seven [Member]
Face value	$ 400,000
Long term debt fixed interest rate percentage	3.75%
Long term debt date of maturity	Jan. 15, 2027
Subsequent Event [Member] | Bxmt Advisory Limited Liability Company And Affiliates [Member] | Three Point Seven Five Senior Secured Notes due Two Thousand Twenty Seven [Member]
Proceeds from long term secured debt	$ 400,000