Regulatory Requirements (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 Minimum	Oct. 31, 2012 Subordinated Debt	Dec. 31, 2012 MS&Co.	Dec. 31, 2011 MS&Co.
Tier 1 capital to RWAs, being well-capitalized for regulatory purposes	6.00%
Total capital to RWAs, being well-capitalized for regulatory purposes	10.00%
Increase of total capital to RWAs ratio	0.65%
Principal amount of debt issued	$ 24,000,000,000		$ 33,000,000,000			$ 2,000,000,000
Tier 1 common capital, ratio	14.60%	[1],[2]	12.60%	[1],[2]	5.00%
Tier 1 leverage ratio, being well-capitalized for regulatory purposes	5.00%
Net capital							7,820,000,000	8,249,000,000
Amount of capital that exceeds the minimum required							6,453,000,000	7,215,000,000
Net capital, minimum amount required to hold							1,000,000,000
Net capital, minimum amount required to hold in accordance with the market and credit risk standards							500,000,000
Amount by which if net capital falls below, the company is required to notify the SEC							5,000,000,000
Net assets of consolidated subsidiaries may be restricted as to the payment of cash dividends and advances to the parent company	$ 17,600,000,000		$ 16,200,000,000

[1] The Company’s December 31, 2011 Tier 1 common capital ratio, Tier 1 capital ratio and Total capital ratio were each reduced by approximately 30 basis points, and Tier 1 leverage ratio was reduced by approximately 20 basis points due to an approximate $1.2 billion deferred tax asset disallowance adjustment, which resulted in a reduction to the Company’s Tier 1 common capital, Tier 1 capital, Total capital, RWAs and adjusted average assets by such amount.

[2] Tier 1 common capital ratio equals Tier 1 common capital divided by RWAs. On December 30, 2011, the Federal Reserve formalized regulatory definitions for Tier 1 common capital and Tier 1 common capital ratio. The Federal Reserve defined Tier 1 common capital as Tier 1 capital less non-common elements in Tier 1 capital, including perpetual preferred stock and related surplus, minority interest in subsidiaries, trust preferred securities and mandatory convertible preferred securities. Previously, the Company’s definition of Tier 1 common capital included all of the items noted in the Federal Reserve’s definition, but it also included an adjustment for the portion of goodwill and non-servicing intangible assets associated with the Wealth Management JV’s noncontrolling interests (i.e., Citi’s share of the Wealth Management JV’s goodwill and intangibles). The Company’s conformance to the Federal Reserve’s definition under the final rule reduced its Tier 1 common capital and Tier 1 common ratio by approximately $4.2 billion and 132 basis points, respectively, at December 31, 2011.