| Cover | Apr. 13, 2020 |
| Schedule of Capitalization, Equity [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 13, 2020 |
| Entity File Number | 1-9924 |
| Entity Registrant Name | Citigroup Inc. |
| Entity Central Index Key | 0000831001 |
| Entity Tax Identification Number | 52-1568099 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 388 Greenwich Street |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10013 |
| City Area Code | (212) |
| Local Phone Number | 559-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $.01 per share |
| Trading Symbol | C |
| Security Exchange Name | NYSE |
| Series J Preferred Stock [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Dep Shs, represent 1/1,000th interest in a share of 7.125% Fix/Float Rate Noncum Pref Stk, Ser J |
| Trading Symbol | C Pr J |
| Security Exchange Name | NYSE |
| Series K Preferred Stock [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Dep Shs, represent 1/1,000th interest in a share of 6.875% Fix/Float Rate Noncum Pref Stk, Ser K |
| Trading Symbol | C Pr K |
| Security Exchange Name | NYSE |
| Series S Preferred Stock [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Depositary Shares, represent 1/1,000th interest in a share of 6.300% Noncum Pref Stock, Ser S |
| Trading Symbol | C Pr S |
| Security Exchange Name | NYSE |
| Citigroup Capital Iii [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 7.625% TRUPs of Cap III (and registrant’s guaranty) |
| Trading Symbol | C/36Y |
| Security Exchange Name | NYSE |
| Citigroup Capital Xiii [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 7.875% FXD / FRN TruPS of Cap XIII (and registrant’s guaranty) |
| Trading Symbol | C N |
| Security Exchange Name | NYSE |
| Citigroup Capital Xviii [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 6.829% FXD / FRN Enhanced TruPS of Cap XVIII (and registrant’s guaranty) |
| Trading Symbol | C/67BP |
| Security Exchange Name | NYSE |
| Ctracks Miller Howard Mlp Fundamental Index [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | C-Tracks ETN Miller/Howard MLP Fundamental Index Due Sept 2023 |
| Trading Symbol | MLPC |
| Security Exchange Name | NYSEArca |
| Ctracks Miller Howard Strategic Dividend Reinvestor [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | C-Tracks ETN Miller/Howard Strategic Dividend Reinvestor Due Sept 2024 |
| Trading Symbol | DIVC |
| Security Exchange Name | NYSEArca |
| Ctracks Miller Howard Mlp Fundamental Index Series B [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | C-Tracks ETN Miller/Howard Fund, Ser B, Due July 2026 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | MLPE |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Usd Vs Jpy [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long USD vs JPY Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | DJPY |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Usd Vs Gbp [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long USD vs GBP Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | DGBP |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Usd Vs Eur [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long USD vs EUR Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | DEUR |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Usd Vs Chf [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long USD vs CHF Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | DCHF |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Usd Vs Aud [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long USD vs AUD Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | DAUD |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Jpy Vs Usd [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long JPY vs USD Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | UJPY |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Eur Vs Usd [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long EUR vs USD Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | UEUR |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Gbp Vs Usd [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long GBP vs USD Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | UGBP |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Chf Vs Usd [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long CHF vs USD Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | UCHF |
| Security Exchange Name | NYSEArca |
| Velocity Shares Daily Long Aud Vs Usd [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | ETN VelocityShares Daily 4X Long AUD vs USD Ind due Dec 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | UAUD |
| Security Exchange Name | NYSEArca |
| Velocity Shares Long Libor Etn [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | VelocityShares Long LIBOR ETNs due Aug 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | ULBR |
| Security Exchange Name | NYSEArca |
| Velocity Shares Short Libor Etn [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | VelocityShares Short LIBOR ETNs due Aug 2032 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | DLBR |
| Security Exchange Name | NYSEArca |
| Series N Medium Term Senior Notes [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | MTN, Series N, Callable Step-Up Coupon Notes Due Mar 2036 of CGMHI (and registrant’s guaranty) |
| Trading Symbol | C/36A |
| Security Exchange Name | NYSE |
| Series G Medium Term Senior Notes [Member] | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | MTN, Series G, Callable Fixed Rate Notes Due Jan 2027 |
| Trading Symbol | C27C |
| Security Exchange Name | NYSE |
