Segment, Geographic and Revenue Information - Selected Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information
Investment banking		$ 10,994	$ 7,674	$ 6,163
Trading		12,810	13,983	11,274
Investments		1,376	986	1,540
Commissions and fees		5,521	4,851	3,919
Asset management		19,967	14,272	13,083
Other		1,042	678	865
Total non-interest revenues		51,710	42,444	36,844
Interest income		9,411	10,162	17,098
Interest expense		1,366	3,849	12,404
Net interest		8,045	6,313	4,694
Net revenues		59,755	48,757	41,538
Provision for credit losses		4	761	161
Compensation and benefits		24,628	20,854	18,837
Non-compensation expenses		15,455	12,724	11,239
Total non-interest expenses		40,083	33,578	30,076
Income from continuing operations before income taxes		19,668	14,418	11,301
Provision for income taxes		4,548	3,239	2,064
Net income		15,120	11,179	9,237
Net income applicable to noncontrolling interests		86	183	195
Net income applicable to Morgan Stanley		15,034	10,996	9,042
Severance-related costs	$ 172
I/E
Segment Reporting Information
Investment banking		(100)	(89)	(80)
Trading		92	76	51
Investments		0	0	0
Commissions and fees		(377)	(376)	(292)
Asset management		(158)	(157)	(158)
Other		(10)	(9)	(6)
Total non-interest revenues		(553)	(555)	(485)
Interest income		(193)	(432)	(582)
Interest expense		(205)	(448)	(600)
Net interest		12	16	18
Net revenues		(541)	(539)	(467)
Provision for credit losses		0	0	0
Compensation and benefits		0	0	0
Non-compensation expenses		(536)	(549)	(461)
Total non-interest expenses		(536)	(549)	(461)
Income from continuing operations before income taxes		(5)	10	(6)
Provision for income taxes		(1)	2	(2)
Net income		(4)	8	(4)
Net income applicable to noncontrolling interests		0	0	0
Net income applicable to Morgan Stanley		(4)	8	(4)
IS
Segment Reporting Information
Severance-related costs	124
IS | Operating Segments
Segment Reporting Information
Investment banking		10,272	7,204	5,734
Trading		12,353	13,097	10,497
Investments		607	166	325
Commissions and fees		2,878	2,935	2,484
Asset management		583	461	413
Other		495	323	563
Total non-interest revenues		27,188	24,186	20,016
Interest income		3,752	5,809	12,193
Interest expense		1,107	3,519	11,713
Net interest		2,645	2,290	480
Net revenues		29,833	26,476	20,496
Provision for credit losses		(7)	731	151
Compensation and benefits		9,165	8,342	7,433
Non-compensation expenses		8,861	8,252	7,422
Total non-interest expenses		18,026	16,594	14,855
Income from continuing operations before income taxes		11,814	9,151	5,490
Provision for income taxes		2,746	2,040	769
Net income		9,068	7,111	4,721
Net income applicable to noncontrolling interests		111	99	122
Net income applicable to Morgan Stanley		8,957	7,012	4,599
WM
Segment Reporting Information
Severance-related costs	37
WM | Operating Segments
Segment Reporting Information
Investment banking		822	559	509
Trading		418	844	734
Investments		48	12	2
Commissions and fees		3,019	2,291	1,726
Asset management		13,966	10,955	10,199
Other		577	403	354
Total non-interest revenues		18,850	15,064	13,524
Interest income		5,821	4,771	5,467
Interest expense		428	749	1,245
Net interest		5,393	4,022	4,222
Net revenues		24,243	19,086	17,746
Provision for credit losses		11	30	10
Compensation and benefits		13,090	10,970	9,774
Non-compensation expenses		4,961	3,699	3,130
Total non-interest expenses		18,051	14,669	12,904
Income from continuing operations before income taxes		6,181	4,387	4,832
Provision for income taxes		1,447	1,026	1,104
Net income		4,734	3,361	3,728
Net income applicable to noncontrolling interests		0	0	0
Net income applicable to Morgan Stanley		4,734	3,361	3,728
IM
Segment Reporting Information
Severance-related costs	$ 11
IM | Operating Segments
Segment Reporting Information
Investment banking		0	0	0
Trading		(53)	(34)	(8)
Investments		721	808	1,213
Commissions and fees		1	1	1
Asset management		5,576	3,013	2,629
Other		(20)	(39)	(46)
Total non-interest revenues		6,225	3,749	3,789
Interest income		31	14	20
Interest expense		36	29	46
Net interest		(5)	(15)	(26)
Net revenues		6,220	3,734	3,763
Provision for credit losses		0	0	0
Compensation and benefits		2,373	1,542	1,630
Non-compensation expenses		2,169	1,322	1,148
Total non-interest expenses		4,542	2,864	2,778
Income from continuing operations before income taxes		1,678	870	985
Provision for income taxes		356	171	193
Net income		1,322	699	792
Net income applicable to noncontrolling interests		(25)	84	73
Net income applicable to Morgan Stanley		$ 1,347	$ 615	$ 719