SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - INTANGIBLE ASSETS AND SEGMENTS (Details) $ / shares in Units, $ in Thousands						9 Months Ended
	Nov. 21, 2018 $ / shares	Nov. 18, 2016 shares	May 17, 2011 shares	May 20, 2008 shares	Nov. 11, 2002 shares	Sep. 30, 2019 USD ($) segment $ / shares shares	Jun. 30, 2019 $ / shares	Mar. 31, 2019 $ / shares	Dec. 31, 2018 $ / shares	Sep. 30, 2018 $ / shares	Jun. 30, 2018 $ / shares	Mar. 31, 2018 $ / shares	Oct. 25, 2000 shares
Income Taxes
Tax benefit | $						$ 0
Common Stock repurchase [Abstract]
Authorized repurchased													200,000
Amount of stock repurchase plan authorized additional		100,000	200,000	200,000	200,000
Number of shares repurchased						764,176
Stock Split
Stock Split ratio	2
Common stock, par value (in dollars per share) | $ / shares	$ 0					$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Operating Segments
Number of reportable operating segments | segment						1
Minimum
Income Taxes
Useful life of core deposit intangible assets						10 years
Maximum
Income Taxes
Useful life of core deposit intangible assets						15 years