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FAIR VALUE DISCLOSURES - Summary of Financial Assets and Liabilities Measure at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Assets
Investment securities available-for-sale	$ 3,753,763
Derivative Asset	226,782		$ 272,499
Liabilities
Derivative liabilities	226,891		272,606
Loans Held-for-sale, Fair Value Disclosure	34,600		41,100
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(1,300)	$ 900
Financing Receivable, Held-for-Sale	30,300		35,500
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables	4,300		5,600
Fair Value, Measurements, Recurring
Assets
Investment securities available-for-sale	3,753,763		3,424,580
Derivative Asset			185,032
Total	4,015,209		3,738,330
Liabilities
Total	227,292		273,739
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 1 \| Fair value
Liabilities
Loans Held-for-sale, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 1
Assets
Investment securities available-for-sale	10,260		103
Derivative Asset			0
Total	10,260		103
Liabilities
Total	0		0
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 2 \| Fair value
Liabilities
Loans Held-for-sale, Fair Value Disclosure	34,590		41,103
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 2
Assets
Investment securities available-for-sale	3,703,825		3,383,902
Derivative Asset			185,032
Total	3,965,271		3,697,652
Liabilities
Total	227,292		273,739
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 3 \| Fair value
Liabilities
Loans Held-for-sale, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 3
Assets
Investment securities available-for-sale	39,678		40,575
Derivative Asset			0
Total	39,678		40,575
Liabilities
Total	0		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1, 2 and 3
Liabilities
Loans Held-for-sale, Fair Value Disclosure	34,590		41,103
Interest Rate Contract [Member] \| Fair Value, Measurements, Recurring
Assets
Derivative Asset	122,156
Liabilities
Derivative liabilities	122,592		186,124
Interest Rate Contract [Member] \| Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 1
Assets
Derivative Asset	0
Liabilities
Derivative liabilities	0		0
Interest Rate Contract [Member] \| Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 2
Assets
Derivative Asset	122,156
Liabilities
Derivative liabilities	122,592		186,124
Interest Rate Contract [Member] \| Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 3
Assets
Derivative Asset	0
Liabilities
Derivative liabilities	0		0
Foreign Exchange [Member] \| Fair Value, Measurements, Recurring
Assets
Derivative Asset	104,700		87,615
Liabilities
Derivative liabilities	104,700		87,615
Foreign Exchange [Member] \| Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 1
Assets
Derivative Asset	0		0
Liabilities
Derivative liabilities	0		0
Foreign Exchange [Member] \| Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 2
Assets
Derivative Asset	104,700		87,615
Liabilities
Derivative liabilities	104,700		87,615
Foreign Exchange [Member] \| Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 3
Assets
Derivative Asset	0		0
Liabilities
Derivative liabilities	$ 0		$ 0