SECURITIES - Total Available for Sale and Held to Maturity Investment Securities by Contractual Maturity (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Fair Value, Total securities
Within One Year	$ 7,422
After One But Within Five Years	64,341
After Five But Within Ten Years	123,940
After Ten Years	641,975
Total Estimated Fair Value	837,678
Amortized Cost, Total securities
Within One Year	7,453
After One But Within Five Years	65,008
After Five But Within Ten	128,612
After Ten Years	656,471
Total Amortized Cost	$ 857,544