LOANS AND ALLOWANCE FOR CREDIT LOSSES (Age Analysis of Past Due Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 3,025,266	$ 5,720,325
Current	93,707,929	88,405,338
Total	96,733,195	94,125,663
Recorded Investment Greater than 90 Days and Accruing	67,152	93,102
LHFS	241,300	289,000
30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,298,533	4,841,015
90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	726,733	879,310
Commercial
Financing Receivable, Past Due [Line Items]
Total	42,573,415	41,151,009
LHFS	1,800,000	116,300
Commercial | CRE
Financing Receivable, Past Due [Line Items]
Total Past Due	193,150	116,762
Current	8,311,839	8,351,261
Total	8,504,989	8,468,023
Recorded Investment Greater than 90 Days and Accruing	0	0
LHFS	1,100,000
Commercial | CRE | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	103,448	51,472
Commercial | CRE | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	89,702	65,290
Commercial | C&I
Financing Receivable, Past Due [Line Items]
Total Past Due	99,219	140,597
Current	18,168,280	16,510,391
Total	18,267,499	16,650,988
Recorded Investment Greater than 90 Days and Accruing	0	0
LHFS	603,000
Commercial | C&I | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	36,285	55,957
Commercial | C&I | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	62,934	84,640
Commercial | Multifamily
Financing Receivable, Past Due [Line Items]
Total Past Due	44,739	14,160
Current	8,564,614	8,627,044
Total	8,609,353	8,641,204
Recorded Investment Greater than 90 Days and Accruing	0	0
LHFS	46,500
Commercial | Multifamily | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	37,575	10,456
Commercial | Multifamily | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	7,164	3,704
Commercial | Other commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	64,108	68,325
Current	7,127,466	7,322,469
Total	7,191,574	7,390,794
Recorded Investment Greater than 90 Days and Accruing	107	0
Commercial | Other commercial | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	56,345	61,973
Commercial | Other commercial | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	7,763	6,352
Consumer | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due	215,215	283,556
Current	8,258,779	8,848,971
Total	8,473,994	9,132,527
Recorded Investment Greater than 90 Days and Accruing	0	0
LHFS	1,000,000	296,800
Consumer | Residential mortgages | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	96,234	154,978
Consumer | Residential mortgages | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	118,981	128,578
Consumer | Home equity loans and lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due	123,245	121,389
Current	4,391,435	4,648,955
Total	4,514,680	4,770,344
Recorded Investment Greater than 90 Days and Accruing	0	0
Consumer | Home equity loans and lines of credit | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	44,406	45,417
Consumer | Home equity loans and lines of credit | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	78,839	75,972
Consumer | RICs and auto loans
Financing Receivable, Past Due [Line Items]
Total Past Due	2,138,470	4,768,833
Current	36,864,123	31,687,914
Total	39,002,593	36,456,747
Recorded Investment Greater than 90 Days and Accruing	0	0
LHFS	1,600,000
Consumer | RICs and auto loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,861,286	4,364,110
Consumer | RICs and auto loans | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	277,184	404,723
Consumer | Personal unsecured loans
Financing Receivable, Past Due [Line Items]
Total Past Due	129,494	187,849
Current	1,769,282	2,110,803
Total	1,898,776	2,298,652
Recorded Investment Greater than 90 Days and Accruing	67,045	93,102
LHFS	1,000,000	1,000,000
Consumer | Personal unsecured loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	53,540	85,277
Consumer | Personal unsecured loans | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	75,954	102,572
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	17,626	18,854
Current	252,111	297,530
Total	269,737	316,384
Recorded Investment Greater than 90 Days and Accruing	0	0
Consumer | Other consumer | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	9,414	11,375
Consumer | Other consumer | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 8,212	$ 7,479