CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities of continuing operations		$ 144	$ 2,093
Cash flows from investing activities of continuing operations
Purchases of investments		(59,715)	(76,463)
Proceeds from sales of investments		39,268	56,928
Proceeds from maturities of investments		16,544	19,897
Change in deposits with banks		(23,852)	(5,807)
Change in loans		(5,057)	6,831
Proceeds from sales and securitizations of loans		1,247	3,259
Proceeds from significant disposals	[1]	265	0
Change in federal funds sold and securities borrowed or purchased under agreements to resell		(5,418)	3,555
Changes in investments and advances—intercompany		0	0
Other investing activities		(472)	(605)
Net cash provided by (used in) investing activities of continuing operations		(37,190)	7,595
Cash flows from financing activities of continuing operations
Dividends paid		(359)	(159)
Issuance of preferred stock		1,004	1,494
Treasury stock acquired		(1,312)	(297)
Proceeds (repayments) from issuance of long-term debt, net		1,941	(3,789)
Proceeds (repayments) from issuance of long-term debt—intercompany, net		0	0
Change in deposits		26,704	315
Change in federal funds purchased and securities loaned or sold under agreements to repurchase		10,712	1,933
Change in short-term borrowings		(186)	(18,930)
Net change in short-term borrowings and other advances—intercompany		0	0
Capital contributions from parent		0
Other financing activities		(308)	(419)
Net cash provided by (used in) financing activities of continuing operations		38,196	(19,852)
Effect of exchange rate changes on cash and cash equivalents		190	(64)
Change in cash and due from banks		1,340	(10,228)
Cash and due from banks at beginning of period		20,900	32,108
Cash and due from banks at end of period		22,240	21,880
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the period for income taxes		688	1,100
Cash paid during the period for interest		2,694	2,908
Non-cash investing activities
Decrease in net loans associated with significant disposals reclassified to HFS		0	(8,735)
Decrease in investments associated with significant disposals reclassified to HFS		0	(1,499)
Decrease in goodwill associated with significant disposals reclassified to HFS		(30)	(184)
Transfers to loans HFS from loans		3,200	14,600
Transfers to OREO and other repossessed assets		56	88
Non-cash financing activities
Decrease in long-term debt due to deconsolidation of VIEs			(4,673)
Reportable legal entities | Citigroup Inc.
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities of continuing operations		5,194	(1,688)
Cash flows from investing activities of continuing operations
Purchases of investments		0	0
Proceeds from sales of investments		0	0
Proceeds from maturities of investments		26	31
Change in deposits with banks		0	0
Change in loans		0	0
Proceeds from sales and securitizations of loans		0	0
Proceeds from significant disposals		0
Change in federal funds sold and securities borrowed or purchased under agreements to resell		0	0
Changes in investments and advances—intercompany		(12,271)	(7,034)
Other investing activities		0	2
Net cash provided by (used in) investing activities of continuing operations		(12,245)	(7,001)
Cash flows from financing activities of continuing operations
Dividends paid		(359)	(159)
Issuance of preferred stock		1,004	1,494
Treasury stock acquired		(1,312)	(297)
Proceeds (repayments) from issuance of long-term debt, net		2,448	1,515
Proceeds (repayments) from issuance of long-term debt—intercompany, net		0	0
Change in deposits		0	0
Change in federal funds purchased and securities loaned or sold under agreements to repurchase		0	0
Change in short-term borrowings		(109)	(400)
Net change in short-term borrowings and other advances—intercompany		5,926	6,966
Capital contributions from parent		0
Other financing activities		(308)	(419)
Net cash provided by (used in) financing activities of continuing operations		7,290	8,700
Effect of exchange rate changes on cash and cash equivalents		0	0
Change in cash and due from banks		239	11
Cash and due from banks at beginning of period		124	125
Cash and due from banks at end of period		363	136
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the period for income taxes		(231)	4
Cash paid during the period for interest		1,036	1,206
Non-cash investing activities
Decrease in net loans associated with significant disposals reclassified to HFS			0
Decrease in investments associated with significant disposals reclassified to HFS			0
Decrease in goodwill associated with significant disposals reclassified to HFS		0	0
Transfers to loans HFS from loans		0	0
Transfers to OREO and other repossessed assets		0	0
Non-cash financing activities
Decrease in long-term debt due to deconsolidation of VIEs			0
Reportable legal entities | CGMHI
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities of continuing operations		(2,833)	(2,682)
Cash flows from investing activities of continuing operations
Purchases of investments		0	0
Proceeds from sales of investments		0	0
Proceeds from maturities of investments		0	0
Change in deposits with banks		(7,380)	(1,453)
Change in loans		0	0
Proceeds from sales and securitizations of loans		0	0
Proceeds from significant disposals		0
Change in federal funds sold and securities borrowed or purchased under agreements to resell		(1,127)	3,929
Changes in investments and advances—intercompany		(6,052)	(12,268)
Other investing activities		0	(20)
Net cash provided by (used in) investing activities of continuing operations		(14,559)	(9,812)
Cash flows from financing activities of continuing operations
Dividends paid		0	0
Issuance of preferred stock		0	0
Treasury stock acquired		0	0
Proceeds (repayments) from issuance of long-term debt, net		1,527	(255)
Proceeds (repayments) from issuance of long-term debt—intercompany, net		(2,692)	13,014
Change in deposits		0	0
Change in federal funds purchased and securities loaned or sold under agreements to repurchase		12,077	2,322
Change in short-term borrowings		342	795
Net change in short-term borrowings and other advances—intercompany		3,711	(2,545)
Capital contributions from parent		2,500
Other financing activities		0	0
Net cash provided by (used in) financing activities of continuing operations		17,465	13,331
Effect of exchange rate changes on cash and cash equivalents		0	0
Change in cash and due from banks		73	837
Cash and due from banks at beginning of period		1,995	1,751
Cash and due from banks at end of period		2,068	2,588
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the period for income taxes		20	44
Cash paid during the period for interest		637	210
Non-cash investing activities
Decrease in net loans associated with significant disposals reclassified to HFS			0
Decrease in investments associated with significant disposals reclassified to HFS			0
Decrease in goodwill associated with significant disposals reclassified to HFS		0	0
Transfers to loans HFS from loans		0	0
Transfers to OREO and other repossessed assets		0	0
Non-cash financing activities
Decrease in long-term debt due to deconsolidation of VIEs			0
Other Citigroup Inc. subsidiaries and eliminations
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities of continuing operations		(2,217)	6,463
Cash flows from investing activities of continuing operations
Purchases of investments		(59,715)	(76,463)
Proceeds from sales of investments		39,268	56,928
Proceeds from maturities of investments		16,518	19,866
Change in deposits with banks		(16,472)	(4,354)
Change in loans		(5,057)	6,831
Proceeds from sales and securitizations of loans		1,247	3,259
Proceeds from significant disposals		265
Change in federal funds sold and securities borrowed or purchased under agreements to resell		(4,291)	(374)
Changes in investments and advances—intercompany		18,323	19,302
Other investing activities		(472)	(587)
Net cash provided by (used in) investing activities of continuing operations		(10,386)	24,408
Cash flows from financing activities of continuing operations
Dividends paid		0	0
Issuance of preferred stock		0	0
Treasury stock acquired		0	0
Proceeds (repayments) from issuance of long-term debt, net		(2,034)	(5,049)
Proceeds (repayments) from issuance of long-term debt—intercompany, net		2,692	(13,014)
Change in deposits		26,704	315
Change in federal funds purchased and securities loaned or sold under agreements to repurchase		(1,365)	(389)
Change in short-term borrowings		(419)	(19,325)
Net change in short-term borrowings and other advances—intercompany		(9,637)	(4,421)
Capital contributions from parent		(2,500)
Other financing activities		0	0
Net cash provided by (used in) financing activities of continuing operations		13,441	(41,883)
Effect of exchange rate changes on cash and cash equivalents		190	(64)
Change in cash and due from banks		1,028	(11,076)
Cash and due from banks at beginning of period		18,781	30,232
Cash and due from banks at end of period		19,809	19,156
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the period for income taxes		899	1,052
Cash paid during the period for interest		1,021	1,492
Non-cash investing activities
Decrease in net loans associated with significant disposals reclassified to HFS			(8,735)
Decrease in investments associated with significant disposals reclassified to HFS			(1,499)
Decrease in goodwill associated with significant disposals reclassified to HFS		(30)	(184)
Transfers to loans HFS from loans		3,200	14,600
Transfers to OREO and other repossessed assets		56	88
Non-cash financing activities
Decrease in long-term debt due to deconsolidation of VIEs			(4,673)
Consolidating adjustments
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities of continuing operations		0	0
Cash flows from investing activities of continuing operations
Purchases of investments		0	0
Proceeds from sales of investments		0	0
Proceeds from maturities of investments		0	0
Change in deposits with banks		0	0
Change in loans		0	0
Proceeds from sales and securitizations of loans		0	0
Proceeds from significant disposals		0
Change in federal funds sold and securities borrowed or purchased under agreements to resell		0	0
Changes in investments and advances—intercompany		0	0
Other investing activities		0	0
Net cash provided by (used in) investing activities of continuing operations		0	0
Cash flows from financing activities of continuing operations
Dividends paid		0	0
Issuance of preferred stock		0	0
Treasury stock acquired		0	0
Proceeds (repayments) from issuance of long-term debt, net		0	0
Proceeds (repayments) from issuance of long-term debt—intercompany, net		0	0
Change in deposits		0	0
Change in federal funds purchased and securities loaned or sold under agreements to repurchase		0	0
Change in short-term borrowings		0	0
Net change in short-term borrowings and other advances—intercompany		0	0
Capital contributions from parent		0
Other financing activities		0	0
Net cash provided by (used in) financing activities of continuing operations		0	0
Effect of exchange rate changes on cash and cash equivalents		0	0
Change in cash and due from banks		0	0
Cash and due from banks at beginning of period		0	0
Cash and due from banks at end of period		0	0
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the period for income taxes		0	0
Cash paid during the period for interest		0	0
Non-cash investing activities
Decrease in net loans associated with significant disposals reclassified to HFS			0
Decrease in investments associated with significant disposals reclassified to HFS			0
Decrease in goodwill associated with significant disposals reclassified to HFS		0	0
Transfers to loans HFS from loans		0	0
Transfers to OREO and other repossessed assets		$ 0	0
Non-cash financing activities
Decrease in long-term debt due to deconsolidation of VIEs			$ 0

[1] See Note 2 for further information on significant disposals.