CHANGE IN ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 1,939,099
Other comprehensive income (loss)	$ (205,059)	$ 24,095	(480,919)	$ (45,221)
Less: Amounts reclassified from accumulated other comprehensive (loss) income	(39)	(155)	(191)	(548)
Net current-period other comprehensive (loss) income	(205,098)	23,940	(481,110)	(45,769)
Ending balance	2,315,360		2,315,360
Amortization of unrealized gain on securities reclassified to held-to-maturity, tax expense	37,830	9	37,839	14
Fannie Mae (FNMA) mortgage-backed securities (MBS)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amortization of unrealized gain on securities reclassified to held-to-maturity, tax expense	119,800
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(313,780)	(13,702)	(37,768)	56,007
Ending balance	(518,878)	10,238	(518,878)	10,238
Net change in investment securities available-for-sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(309,791)	(9,957)	(33,873)	59,882
Other comprehensive income (loss)	(85,422)	24,104	(361,340)	(45,485)
Less: Amounts reclassified from accumulated other comprehensive (loss) income	0	0	0	(250)
Net current-period other comprehensive (loss) income	(85,422)	24,104	(361,340)	(45,735)
Ending balance	(395,213)	14,147	(395,213)	14,147
Net change in investment securities held-to-maturity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	147	260	175	276
Other comprehensive income (loss)	(119,824)	0	(119,768)	0
Less: Amounts reclassified from accumulated other comprehensive (loss) income	28	(28)	(56)	(44)
Net current-period other comprehensive (loss) income	(119,796)	(28)	(119,824)	(44)
Ending balance	(119,649)	232	(119,649)	232
Net change in defined benefit plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,718)	(4,804)	(4,691)	(4,788)
Other comprehensive income (loss)	(1)	(9)	0	(9)
Less: Amounts reclassified from accumulated other comprehensive (loss) income	(27)	(15)	(55)	(31)
Net current-period other comprehensive (loss) income	(28)	(24)	(55)	(40)
Ending balance	(4,746)	(4,828)	(4,746)	(4,828)
Net change in fair value of derivatives used for cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	229	535	268	646
Other comprehensive income (loss)	0	0	1	0
Less: Amounts reclassified from accumulated other comprehensive (loss) income	(40)	(112)	(80)	(223)
Net current-period other comprehensive (loss) income	(40)	(112)	(79)	(223)
Ending balance	189	423	189	423
Net change in equity method investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	353	264	353	(9)
Other comprehensive income (loss)	188	0	188	273
Less: Amounts reclassified from accumulated other comprehensive (loss) income	0	0	0	0
Net current-period other comprehensive (loss) income	188	0	188	273
Ending balance	$ 541	$ 264	$ 541	$ 264

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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