LOANS AND ALLOWANCE FOR CREDIT LOSSES (Troubled Debt Restructuring Activity) (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) contract	Jun. 30, 2019 USD ($) contract	Jun. 30, 2020 USD ($) contract	Jun. 30, 2019 USD ($) contract	Dec. 31, 2019 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings	$ 4,300,095		$ 4,300,095		$ 4,320,131
Number of Contracts \| contract	46,235	17,488	56,143	37,501
Pre-TDR Recorded Investment	$ 1,019,795	$ 303,589	$ 1,204,109	$ 688,321
Post-TDR Recorded Investment	$ 1,036,089	$ 304,699	$ 1,220,946	$ 691,730
TDRs which Subsequently Defaulted
Number of Contracts \| contract	2,086	5,429	6,223	13,123
Recorded Investment	$ 41,696	$ 94,209	$ 123,647	$ 226,013
Commercial \| CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	9	8	11	25
Pre-TDR Recorded Investment	$ 13,047	$ 423	$ 14,974	$ 45,131
Post-TDR Recorded Investment	$ 13,047	$ 416	$ 14,974	$ 46,230
TDRs which Subsequently Defaulted
Number of Contracts \| contract	14	1	32	2
Recorded Investment	$ 2,909	$ 93	$ 5,114	$ 223
Commercial \| C&I
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	354	14	389	38
Pre-TDR Recorded Investment	$ 27,130	$ 318	$ 27,965	$ 938
Post-TDR Recorded Investment	$ 27,226	$ 317	$ 28,063	$ 938
TDRs which Subsequently Defaulted
Number of Contracts \| contract	5	10	16	25
Recorded Investment	$ 1,045	$ 254	$ 8,260	$ 845
Commercial \| Multifamily
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	5		5
Pre-TDR Recorded Investment	$ 51,466		$ 51,466
Post-TDR Recorded Investment	$ 51,466		$ 51,466
Commercial \| Other commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	4		5
Pre-TDR Recorded Investment	$ 72		$ 117
Post-TDR Recorded Investment	$ 72		$ 117
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	15	22	28	48
Pre-TDR Recorded Investment	$ 1,811	$ 4,011	$ 3,672	$ 7,524
Post-TDR Recorded Investment	$ 1,809	$ 4,088	$ 3,814	$ 7,758
TDRs which Subsequently Defaulted
Number of Contracts \| contract	22	26	30	79
Recorded Investment	$ 3,640	$ 2,826	$ 4,880	$ 7,628
Consumer \| Home equity loans and lines of credit
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	22	35	50	75
Pre-TDR Recorded Investment	$ 2,693	$ 2,863	$ 4,767	$ 7,858
Post-TDR Recorded Investment	$ 2,939	$ 3,181	$ 5,034	$ 8,597
TDRs which Subsequently Defaulted
Number of Contracts \| contract	10	9	22	15
Recorded Investment	$ 1,142	$ 641	$ 3,104	$ 1,066
Consumer \| RICs and auto loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	45,060	17,322	54,855	37,171
Pre-TDR Recorded Investment	$ 896,193	$ 294,796	$ 1,072,573	$ 624,938
Post-TDR Recorded Investment	$ 911,804	$ 295,513	$ 1,088,570	$ 626,273
TDRs which Subsequently Defaulted
Number of Contracts \| contract	2,000	5,326	6,076	12,885
Recorded Investment	$ 31,441	$ 89,749	$ 100,437	$ 215,071
Consumer \| Personal unsecured loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	1	74	2	125
Pre-TDR Recorded Investment	$ 0	$ 736	$ 0	$ 1,307
Post-TDR Recorded Investment	$ 0	$ 745	$ 0	$ 1,313
TDRs which Subsequently Defaulted
Number of Contracts \| contract	0	57	0	117
Recorded Investment	$ 0	$ 646	$ 0	$ 1,180
Consumer \| Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| contract	765	13	798	19
Pre-TDR Recorded Investment	$ 27,383	$ 442	$ 28,575	$ 625
Post-TDR Recorded Investment	$ 27,726	$ 439	$ 28,908	$ 621
TDRs which Subsequently Defaulted
Number of Contracts \| contract	35	0	46	0
Recorded Investment	$ 1,519	$ 0	$ 1,807	$ 0
Performing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings	3,850,850		3,850,850		3,646,354
Non-performing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings	$ 449,245		$ 449,245		$ 673,777

Financing Receivable, Modifications, Subsequent Default [Abstract]

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-Publisher FASB
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