MARKETABLE SECURITIES - Contractual Maturities of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Amortized Cost
Due within one year	$ 0
Due after one year through five years	14,620
Due after five years through ten years	30,447
Due after ten years	0
Available-for-sale debt securities, amortized cost basis	326,646	$ 341,628
Estimated Fair Value
Due within one year	0
Due after one year through five years	14,647
Due after five years through ten years	29,130
Due after ten years	0
Available-for-sale debt securities, estimated fair value	306,704	342,206
Held to Maturity Amortized Cost
Due within one year	233,817
Due after one year through five years	98,824
Due after five years through ten years	53,743
Due after ten years	75,618
Held to Maturity debt securities, amortized cost	494,289	184,263
Held to Maturity Estimated Fair Value
Due within one year	233,217
Due after one year through five years	98,980
Due after five years through ten years	53,495
Due after ten years	74,078
Held to maturity debt securities, estimated fair value	490,523	192,472
Mortgage-backed securities
Amortized Cost
Available-for-sale debt securities, amortized cost basis	212,489
Available-for-sale debt securities, amortized cost basis	212,489	221,610
Estimated Fair Value
Available-for-sale debt securities, estimated fair value	197,892
Available-for-sale debt securities, estimated fair value	197,892	221,308
Held to Maturity Amortized Cost
Held to Maturity debt securities, amortized cost	32,287
Held to Maturity debt securities, amortized cost	32,287	2,953
Held to Maturity Estimated Fair Value
Held to maturity debt securities, estimated fair value	30,753
Held to maturity debt securities, estimated fair value	30,753	2,916
Collateralized mortgage obligations
Amortized Cost
Available-for-sale debt securities, amortized cost basis	69,090
Available-for-sale debt securities, amortized cost basis	69,090	74,925
Estimated Fair Value
Available-for-sale debt securities, estimated fair value	65,035
Available-for-sale debt securities, estimated fair value	65,035	$ 74,992
Held to Maturity Amortized Cost
Held to Maturity debt securities, amortized cost	0
Held to Maturity Estimated Fair Value
Held to maturity debt securities, estimated fair value	$ 0