LOANS AND ALLOWANCE FOR CREDIT LOSSES (Troubled Debt Restructuring Activity) (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 USD ($) contract	Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 USD ($) contract	Dec. 31, 2019 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings	$ 4,239,197		$ 4,239,197		$ 4,320,131
Number of Contracts \| contract	15,220	21,715	71,363	59,203
Pre-TDR Recorded Investment	$ 400,351	$ 400,739	$ 1,604,460	$ 1,088,092
Post-TDR Recorded Investment	$ 401,997	$ 397,651	$ 1,622,945	$ 1,088,397
TDRs which Subsequently Defaulted
Number of Contracts \| contract	4,429	5,287	10,652	18,410
Recorded Investment	$ 88,162	$ 93,497	$ 211,810	$ 319,510
Commercial \| CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	20	12	31	37
Pre-TDR Recorded Investment	$ 33,898	$ 15,388	$ 48,872	$ 60,520
Post-TDR Recorded Investment	$ 33,898	$ 10,061	$ 48,872	$ 56,291
TDRs which Subsequently Defaulted
Number of Contracts \| contract	2	0	34	2
Recorded Investment	$ 3,011	$ 0	$ 8,125	$ 223
Commercial \| C&I
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	126	23	515	61
Pre-TDR Recorded Investment	$ 22,611	$ 651	$ 50,576	$ 1,589
Post-TDR Recorded Investment	$ 22,631	$ 655	$ 50,694	$ 1,593
TDRs which Subsequently Defaulted
Number of Contracts \| contract	26	6	42	31
Recorded Investment	$ 905	$ 5,956	$ 9,165	$ 6,801
Commercial \| Multifamily
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	0		5
Pre-TDR Recorded Investment	$ 0		$ 51,466
Post-TDR Recorded Investment	$ 0		$ 51,466
Commercial \| Other commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	4		9
Pre-TDR Recorded Investment	$ 894		$ 1,011
Post-TDR Recorded Investment	$ 894		$ 1,011
TDRs which Subsequently Defaulted
Number of Contracts \| contract	0	0	1	0
Recorded Investment	$ 0	$ 0	$ 45	$ 0
Consumer \| Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	161	29	189	74
Pre-TDR Recorded Investment	$ 12,422	$ 3,822	$ 16,094	$ 10,497
Post-TDR Recorded Investment	$ 12,419	$ 3,857	$ 16,234	$ 10,767
TDRs which Subsequently Defaulted
Number of Contracts \| contract	3	23	33	102
Recorded Investment	$ 397	$ 2,804	$ 5,278	$ 10,432
Consumer \| Home equity loans and lines of credit
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	21	30	71	107
Pre-TDR Recorded Investment	$ 2,189	$ 2,676	$ 6,956	$ 10,684
Post-TDR Recorded Investment	$ 2,295	$ 3,313	$ 7,329	$ 12,041
TDRs which Subsequently Defaulted
Number of Contracts \| contract	0	9	22	24
Recorded Investment	$ 0	$ 641	$ 3,104	$ 1,707
Consumer \| RICs and auto loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	14,530	21,553	69,385	58,724
Pre-TDR Recorded Investment	$ 313,816	$ 376,520	$ 1,386,389	$ 1,001,458
Post-TDR Recorded Investment	$ 315,368	$ 378,063	$ 1,403,939	$ 1,004,336
TDRs which Subsequently Defaulted
Number of Contracts \| contract	4,353	5,188	10,429	18,073
Recorded Investment	$ 82,098	$ 83,531	$ 182,535	$ 298,602
Consumer \| Personal unsecured loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	2	40	4	161
Pre-TDR Recorded Investment	$ 7	$ 633	$ 7	$ 1,938
Post-TDR Recorded Investment	$ 0	$ 659	$ 0	$ 1,972
TDRs which Subsequently Defaulted
Number of Contracts \| contract	0	61	0	178
Recorded Investment	$ 0	$ 565	$ 0	$ 1,745
Consumer \| Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	356	28	1,154	39
Pre-TDR Recorded Investment	$ 14,514	$ 1,049	$ 43,089	$ 1,406
Post-TDR Recorded Investment	$ 14,492	$ 1,043	$ 43,400	$ 1,397
TDRs which Subsequently Defaulted
Number of Contracts \| contract	45	0	91	0
Recorded Investment	$ 1,751	$ 0	$ 3,558	$ 0
Performing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings	3,710,124		3,710,124		3,646,354
Non-performing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings	$ 529,073		$ 529,073		$ 673,777

Financing Receivable, Modifications, Subsequent Default [Abstract]

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-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
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