Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Results
Total non-interest revenues	$ 7,559	$ 8,936	$ 9,704	$ 10,102	$ 8,505	$ 8,414	$ 8,752	$ 8,974	$ 36,301	$ 34,645	$ 30,933
Net interest	989	936	906	975	995	783	751	771	3,806	3,300	3,698
Net revenues	8,548	9,872	10,610	11,077	9,500	9,197	9,503	9,745	40,107	37,945	34,631
Total non-interest expenses	6,691	7,021	7,501	7,657	7,029	6,715	6,861	6,937	28,870	27,542	25,783
Income from continuing operations before income taxes	1,857	2,851	3,109	3,420	2,471	2,482	2,642	2,808	11,237	10,403	8,848
Provision for income taxes	300	696	640	714	1,810	697	846	815	2,350	4,168	2,726
Income (loss) from continuing operations	1,557	2,155	2,469	2,706	661	1,785	1,796	1,993	8,887	6,235	6,122
Income (loss) from discontinued operations	1	(1)	(2)	(2)	2	6	(5)	(22)	(4)	(19)	1
Net income	1,558	2,154	2,467	2,704	663	1,791	1,791	1,971	8,883	6,216	6,123
Net income applicable to noncontrolling interests	27	42	30	36	20	10	34	41	135	105	144
Net income applicable to Morgan Stanley	1,531	2,112	2,437	2,668	643	1,781	1,757	1,930	8,748	6,111	5,979
Preferred stock dividends and other	170	93	170	93	170	93	170	90	526	523	471
Earnings applicable to Morgan Stanley common shareholders	$ 1,361	$ 2,019	$ 2,267	$ 2,575	$ 473	$ 1,688	$ 1,587	$ 1,840	$ 8,222	$ 5,588	$ 5,508
Earnings (loss) per basic common share:
Income from continuing operations	$ 0.81	$ 1.19	$ 1.32	$ 1.48	$ 0.27	$ 0.95	$ 0.89	$ 1.03	$ 4.81	$ 3.15	$ 2.98
Income (loss) from discontinued operations	0	0	0	0	0	0	0	(0.01)	0	(0.01)	0
Earnings per basic common share	0.81	1.19	1.32	1.48	0.27	0.95	0.89	1.02	4.81	3.14	2.98
Earnings (loss) per diluted common share:
Income from continuing operations	0.8	1.17	1.3	1.46	0.26	0.93	0.87	1.01	4.73	3.08	2.92
Income (loss) from discontinued operations	0	0	0	(0.01)	0	0	0	(0.01)	0	(0.01)	0
Earnings per diluted common share	0.8	1.17	1.3	1.45	0.26	0.93	0.87	1	4.73	3.07	2.92
Dividends declared per common share	0.3	0.3	0.25	0.25	0.25	0.25	0.2	0.2	$ 1.1	$ 0.9	$ 0.7
Book value per common share	$ 42.2	$ 40.67	$ 40.34	$ 39.19	$ 38.52	$ 38.87	$ 38.22	$ 37.48