Partnership Capital Subject to Mandatory Redemption - Roll Forward of Outstanding Partnership Loans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Partners' Capital Notes [Abstract]
Partnership loans outstanding at beginning of year	$ 439	$ 335	$ 321
Partnership loans issued during the year	270	319	276
Repayment of Partnership loans during the year	(236)	(215)
Partnership loans outstanding	$ 473	$ 439	$ 335