Consolidated Statements of Changes in Partnership Capital Subject to Mandatory Redemption - USD ($) $ in Millions	Total	Limited Partnership Capital [Member]	Subordinated Limited Partnership Capital [Member]	General Partnership Capital [Member]
TOTAL PARTNERSHIP CAPITAL SUBJECT TO MANDATORY REDEMPTION at Dec. 31, 2017	$ 2,795	$ 956	$ 499	$ 1,340
Reserve for anticipated withdrawals at Dec. 31, 2017	(290)	(66)	(36)	(188)
Partnership capital subject to mandatory redemption, net of reserve for anticipated withdrawals at Dec. 31, 2017	2,505	890	463	1,152
Partnership loans outstanding at beginning of year at Dec. 31, 2017	297	0	3	294
Total partnership capital, including capital financed with partnership loans, net of reserve for anticipated withdrawals at Dec. 31, 2017	2,802	890	466	1,446
Issuance of partnership interests	230	5	53	172
Redemption of partnership interests	(296)	(11)	(11)	(274)
Income allocated to partners	990	114	127	749
Distributions	(539)	(42)	(86)	(411)
Total partnership capital, including capital financed with partnership loans at Dec. 31, 2018	3,187	956	549	1,682
Partnership loans outstanding, reduction to arrive at Partnership Capital at Dec. 31, 2018	(332)	0	(4)	(328)
TOTAL PARTNERSHIP CAPITAL SUBJECT TO MANDATORY REDEMPTION at Dec. 31, 2018	2,855	956	545	1,354
Reserve for anticipated withdrawals at Dec. 31, 2018	(348)	(72)	(41)	(235)
Partnership capital subject to mandatory redemption, net of reserve for anticipated withdrawals at Dec. 31, 2018	2,507	884	504	1,119
Partnership loans outstanding at end of year at Dec. 31, 2018	332	0	4	328
Total partnership capital, including capital financed with partnership loans, net of reserve for anticipated withdrawals at Dec. 31, 2018	2,839	884	508	1,447
Issuance of partnership interests	596	380	53	163
Redemption of partnership interests	(228)	(15)	(34)	(179)
Income allocated to partners	1,092	166	130	796
Distributions	(575)	(56)	(87)	(432)
Total partnership capital, including capital financed with partnership loans at Dec. 31, 2019	3,724	1,359	570	1,795
Partnership loans outstanding, reduction to arrive at Partnership Capital at Dec. 31, 2019	(360)	0	(4)	(356)
TOTAL PARTNERSHIP CAPITAL SUBJECT TO MANDATORY REDEMPTION at Dec. 31, 2019	3,364	1,359	566	1,439
Reserve for anticipated withdrawals at Dec. 31, 2019	(407)	(110)	(43)	(254)
Partnership capital subject to mandatory redemption, net of reserve for anticipated withdrawals at Dec. 31, 2019	2,957	1,249	523	1,185
Partnership loans outstanding at end of year at Dec. 31, 2019	360	0	4	356
Total partnership capital, including capital financed with partnership loans, net of reserve for anticipated withdrawals at Dec. 31, 2019	3,317	1,249	527	1,541
Issuance of partnership interests	213	1	49	163
Redemption of partnership interests	(244)	(13)	(37)	(194)
Income allocated to partners	1,285	189	149	947
Distributions	(641)	(64)	(93)	(484)
Total partnership capital, including capital financed with partnership loans at Dec. 31, 2020	3,930	1,362	595	1,973
Partnership loans outstanding, reduction to arrive at Partnership Capital at Dec. 31, 2020	(341)	0	(1)	(340)
TOTAL PARTNERSHIP CAPITAL SUBJECT TO MANDATORY REDEMPTION at Dec. 31, 2020	3,589	1,362	594	1,633
Reserve for anticipated withdrawals at Dec. 31, 2020	(514)	(125)	(56)	(333)
Partnership capital subject to mandatory redemption, net of reserve for anticipated withdrawals at Dec. 31, 2020	3,075	$ 1,237	$ 538	$ 1,300
Partnership loans outstanding at end of year at Dec. 31, 2020	$ 341