LOANS AND ALLOWANCE FOR CREDIT LOSSES (Lending Asset Quality Indicators) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 96,733,195	$ 94,125,663
LHFS	241,300	289,000
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,347,547
2019	9,727,190
2018	8,215,548
2017	4,798,497
2016	3,170,278
Prior	9,314,355
Total	42,573,415	41,151,009
LHFS	1,800,000	116,300
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,077,471
2019	9,033,763
2018	7,536,527
2017	4,244,959
2016	2,704,226
Prior	7,649,894
Total	38,246,840	37,758,696
Commercial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	30,477
2019	270,022
2018	381,228
2017	390,879
2016	278,143
Prior	1,008,691
Total	2,359,440	1,772,410
Commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	36,884
2019	52,691
2018	198,022
2017	136,577
2016	158,903
Prior	580,958
Total	1,164,035	770,023
Commercial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	691
2019	0
2018	121
2017	3,988
2016	618
Prior	2,113
Total	7,531	85,129
Commercial | N/A
Financing Receivable, Credit Quality Indicator [Line Items]
2020	202,024
2019	370,714
2018	99,650
2017	22,094
2016	28,388
Prior	72,699
Total	795,569	764,751
Commercial | CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2020	261,854
2019	1,326,064
2018	1,866,719
2017	1,498,336
2016	1,052,339
Prior	2,499,677
Total	8,504,989	8,468,023
LHFS	1,100,000
Commercial | CRE | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	260,691
2019	1,183,498
2018	1,746,022
2017	1,319,696
2016	853,268
Prior	1,964,698
Total	7,327,873	7,513,567
Commercial | CRE | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,163
2019	125,290
2018	90,447
2017	146,761
2016	119,398
Prior	268,717
Total	751,776	508,133
Commercial | CRE | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	17,276
2018	30,250
2017	31,879
2016	79,673
Prior	262,281
Total	421,359	379,199
Commercial | CRE | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	306
Total	306	24,378
Commercial | CRE | N/A
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	3,675
Total	3,675	42,746
Commercial | C&I
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,813,691
2019	4,420,541
2018	3,471,104
2017	1,189,077
2016	810,834
Prior	3,562,252
Total	18,267,499	16,650,988
LHFS	603,000
Commercial | C&I | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,554,855
2019	3,893,807
2018	2,977,262
2017	977,492
2016	590,003
Prior	2,814,553
Total	15,807,972	14,816,669
Commercial | C&I | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	19,708
2019	125,414
2018	232,373
2017	145,859
2016	123,415
Prior	431,816
Total	1,078,585	743,462
Commercial | C&I | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	36,413
2019	30,606
2018	161,818
2017	39,673
2016	68,624
Prior	245,123
Total	582,257	321,842
Commercial | C&I | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	691
2019	0
2018	1
2017	3,959
2016	404
Prior	1,736
Total	6,791	47,010
Commercial | C&I | N/A
Financing Receivable, Credit Quality Indicator [Line Items]
2020	202,024
2019	370,714
2018	99,650
2017	22,094
2016	28,388
Prior	69,024
Total	791,894	722,005
Commercial | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2020	596,068
2019	2,100,902
2018	1,850,289
2017	1,419,773
2016	607,433
Prior	2,034,888
Total	8,609,353	8,641,204
LHFS	46,500
Commercial | Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	596,068
2019	2,080,706
2018	1,802,434
2017	1,283,891
2016	583,711
Prior	1,929,736
Total	8,276,546	8,356,377
Commercial | Multifamily | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	16,408
2018	47,855
2017	82,368
2016	21,972
Prior	65,259
Total	233,862	260,764
Commercial | Multifamily | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	3,788
2018	0
2017	53,514
2016	1,750
Prior	39,893
Total	98,945	24,063
Commercial | Multifamily | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	0	0
Commercial | Multifamily | N/A
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	0	0
Commercial | Remaining commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,675,934
2019	1,879,683
2018	1,027,436
2017	691,311
2016	699,672
Prior	1,217,538
Total	7,191,574	7,390,794
Commercial | Remaining commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,665,857
2019	1,875,752
2018	1,010,809
2017	663,880
2016	677,244
Prior	940,907
Total	6,834,449	7,072,083
Commercial | Remaining commercial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	9,606
2019	2,910
2018	10,553
2017	15,891
2016	13,358
Prior	242,899
Total	295,217	260,051
Commercial | Remaining commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	471
2019	1,021
2018	5,954
2017	11,511
2016	8,856
Prior	33,661
Total	61,474	44,919
Commercial | Remaining commercial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	120
2017	29
2016	214
Prior	71
Total	434	13,741
Commercial | Remaining commercial | N/A
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	$ 0	$ 0