SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Dividends
Period from which net retained earnings are available for dividend payment from the Bank to the Parent Company	2 years
Amount up to which dividends can be declared by the Bank to the Parent Company	$ 58,700
Cash dividends paid	24,500
Income Taxes
Unrecognized Tax Benefits	$ 0		$ 0
Segment Reporting
Number of reportable operating segment | segment	1
Leases
Operating lease right-of-use assets	$ 43,450
Operating Lease, Liability	$ 45,977
ASU 2016-02 | Measurement Period Adjustments
Leases
Operating lease right-of-use assets		$ 39,000
Operating Lease, Liability		$ 39,000
Core deposit intangibles
Summary Of Accounting Policies [Line Items]
Intangible assets, useful life (in years)	10 years
Buildings
Summary Of Accounting Policies [Line Items]
Useful life	50 years
Equipment, computer hardware and software and furniture and fixtures | Minimum
Summary Of Accounting Policies [Line Items]
Useful life	2 years
Equipment, computer hardware and software and furniture and fixtures | Maximum
Summary Of Accounting Policies [Line Items]
Useful life	10 years