FAIR VALUE MEASURES - Loans Held for Sale Under the Fair Value Option (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, fair value	$ 1,368,044	$ 1,656,711
Mortgage loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, fair value	1,348,193	1,647,900
SBA loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, fair value	$ 19,851	$ 8,811