SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares	Jan. 01, 2023 USD ($)	Dec. 31, 2020 USD ($)
Other Investments
Interest receivable	$ 7,500	$ 7,700
Debt securities held-to-maturity, at amortized cost	141,512	134,864
Held-to-maturity securities	0	0
Other investments	71,794	110,992
Allowance for Credit Losses
Interest receivable	$ 7,500	7,700
Leases
Initial lease terms (in years)	13 years
Share-based Compensation
Company stock-based compensation cost	$ 10,000	$ 6,700	$ 7,900
Earnings Per Share
Anti-dilutive common shares excluded (in shares) | shares		0	0
Operating Segments
Number of reportable segments | segment	5
Accounting Standards Adopted
Allowance for credit losses	$ (307,100)	$ (205,677)	$ (167,582)		$ (199,422)
Retained earnings (accumulated deficit)	$ 1,539,957	1,311,258
Cumulative Effect, Period of Adoption, Adjusted Balance
Accounting Standards Adopted
Allowance for credit losses				$ 1,700
Retained earnings (accumulated deficit)				$ 1,300
Minimum | Core deposit premiums
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	7 years
Maximum | Core deposit premiums
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	10 years
Financing Receivable
Other Investments
Interest receivable	$ 79,200	69,300
Allowance for Credit Losses
Interest receivable	$ 79,200	$ 69,300
Buildings and leasehold improvements | Maximum
Premises and Equipment
Estimated useful lives, premises and equipment (in years)	40 years
Furniture and equipment | Minimum
Premises and Equipment
Estimated useful lives, premises and equipment (in years)	3 years
Furniture and equipment | Maximum
Premises and Equipment
Estimated useful lives, premises and equipment (in years)	20 years
Software And Computer Equipment | Minimum
Premises and Equipment
Estimated useful lives, premises and equipment (in years)	3 years
Software And Computer Equipment | Maximum
Premises and Equipment
Estimated useful lives, premises and equipment (in years)	5 years
US Premium Financing Holding Company | Minimum | Referral relationships
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	8 years
US Premium Financing Holding Company | Minimum | Trade names
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	5 years
US Premium Financing Holding Company | Minimum | Non-compete agreements
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	3 years
US Premium Financing Holding Company | Maximum | Referral relationships
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	10 years
US Premium Financing Holding Company | Maximum | Trade names
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	7 years
US Premium Financing Holding Company | Maximum | Non-compete agreements
Goodwill and Intangible Assets
Acquired finite-lived intangible assets, weighted average useful life (in years)	10 years
Visa Class B Shares
Other Investments
Shares held in other investment (in shares) | shares	57,611
Other investments	$ 242,000
Conversation ratio	1.5875