FAIR VALUE (Fair Value Measurements, Recurring) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financial assets:
AFS investment securities	$ 12,047,923	$ 14,339,758
Other investments - trading securities	19,766	1,097
RICs held-for-investment	72,900	102,000
LHFS	241,300	289,000
Other assets - derivatives	1,644,784	555,896
Financial liabilities:
Other liabilities - derivatives	1,424,258	537,008
Total MSRs	90,231	132,683
U.S. Treasury securities
Financial assets:
AFS investment securities	1,521,795	4,090,938
Corporate debt
Financial assets:
AFS investment securities	98,486	139,713
ABS
Financial assets:
AFS investment securities	113,265	138,400
State and municipal securities
Financial assets:
AFS investment securities	5	9
Recurring
Financial assets:
AFS investment securities	12,047,923	14,339,758
Other investments - trading securities	19,766	1,097
RICs held-for-investment	72,862	101,968
LHFS	241,250	289,009
MSRs	88,674	130,855
Other assets - derivatives	1,645,386	556,331
Total financial assets	14,115,861	15,419,018
Financial liabilities:
Other liabilities - derivatives	1,434,883	546,414
Total financial liabilities	1,434,883	546,414
Recurring \| U.S. Treasury securities
Financial assets:
AFS investment securities	1,521,795	4,090,938
Recurring \| Corporate debt
Financial assets:
AFS investment securities	98,486	139,713
Recurring \| ABS
Financial assets:
AFS investment securities	113,265	138,400
Recurring \| State and municipal securities
Financial assets:
AFS investment securities	5	9
Recurring \| MBS
Financial assets:
AFS investment securities	10,314,372	9,970,698
Recurring \| Level 1
Financial assets:
AFS investment securities	0	0
Other investments - trading securities	0	379
RICs held-for-investment	0	0
LHFS	0	0
MSRs	0	0
Other assets - derivatives	0	0
Total financial assets	0	379
Financial liabilities:
Other liabilities - derivatives	0	0
Total financial liabilities	0	0
Recurring \| Level 1 \| U.S. Treasury securities
Financial assets:
AFS investment securities	0	0
Recurring \| Level 1 \| Corporate debt
Financial assets:
AFS investment securities	0	0
Recurring \| Level 1 \| ABS
Financial assets:
AFS investment securities	0	0
Recurring \| Level 1 \| State and municipal securities
Financial assets:
AFS investment securities	0	0
Recurring \| Level 1 \| MBS
Financial assets:
AFS investment securities	0	0
Recurring \| Level 2
Financial assets:
AFS investment securities	11,997,259	14,276,523
Other investments - trading securities	19,766	718
RICs held-for-investment	0	17,634
LHFS	241,250	289,009
MSRs	0	0
Other assets - derivatives	1,628,619	553,222
Total financial assets	13,886,894	15,137,106
Financial liabilities:
Other liabilities - derivatives	1,428,086	543,560
Total financial liabilities	1,428,086	543,560
Recurring \| Level 2 \| U.S. Treasury securities
Financial assets:
AFS investment securities	1,521,795	4,090,938
Recurring \| Level 2 \| Corporate debt
Financial assets:
AFS investment securities	98,486	139,713
Recurring \| Level 2 \| ABS
Financial assets:
AFS investment securities	62,601	75,165
Recurring \| Level 2 \| State and municipal securities
Financial assets:
AFS investment securities	5	9
Recurring \| Level 2 \| MBS
Financial assets:
AFS investment securities	10,314,372	9,970,698
Recurring \| Level 3
Financial assets:
AFS investment securities	50,664	63,235
Other investments - trading securities	0	0
RICs held-for-investment	72,862	84,334
LHFS	0	0
MSRs	88,674	130,855
Other assets - derivatives	16,767	3,109
Total financial assets	228,967	281,533
Financial liabilities:
Other liabilities - derivatives	6,797	2,854
Total financial liabilities	$ 6,797	2,854
Percentage of level 3 assets to total assets held at fair value	1.60%
Percentage of level 3 assets to total assets	0.20%
Recurring \| Level 3 \| U.S. Treasury securities
Financial assets:
AFS investment securities	$ 0	0
Recurring \| Level 3 \| Corporate debt
Financial assets:
AFS investment securities	0	0
Recurring \| Level 3 \| ABS
Financial assets:
AFS investment securities	50,664	63,235
Recurring \| Level 3 \| State and municipal securities
Financial assets:
AFS investment securities	0	0
Recurring \| Level 3 \| MBS
Financial assets:
AFS investment securities	$ 0	$ 0

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Percentage of Level 3 assets to total assets held at fair value

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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