DEBT - Trust Preferred Securities (Details) - Jun. 30, 2015 - USD ($) $ in Millions	Total
Trust Preferred Securities
Liquidation value	$ 2,597
Junior subordinated debentures owned by the Trust, amount	$ 2,603
Citigroup Capital III
Trust Preferred Securities
Securities issued (in shares)	194,053
Liquidation value	$ 194
Coupon rate (as a percent)	7.625%
Common shares issued to parent (in shares)	6,003
Junior subordinated debentures owned by the Trust, amount	$ 200
Citigroup Capital XIII
Trust Preferred Securities
Securities issued (in shares)	89,840,000
Liquidation value	$ 2,246
Coupon rate (as a percent)	7.875%
Common shares issued to parent (in shares)	1,000
Junior subordinated debentures owned by the Trust, amount	$ 2,246
Citigroup Capital XVIII
Trust Preferred Securities
Securities issued (in shares)	99,901
Liquidation value	$ 157
Coupon rate (as a percent)	6.829%
Common shares issued to parent (in shares)	50
Junior subordinated debentures owned by the Trust, amount	$ 157