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SECURITIES - Summary of Securities Available for Sale and Held to Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Securities available for sale
Amortized Cost	$ 1,297,339	$ 1,421,273
Gross Unrealized Gains	16,503	4,065
Gross Unrealized Losses	(2,287)	(25,691)
Securities available for sale, at fair value	1,311,555	1,399,647
Securities held to maturity
Amortized Cost	357,979	373,763
Gross Unrealized Gains	16,263	4,124
Gross Unrealized Losses	(965)	(6,663)
Fair Value	373,277	371,224
Marketable equity securities, amortized cost	37,138	55,471
Marketable equity securities, gross unrealized gains	5,147	4,370
Marketable equity securities, gross unrealized losses	(729)	(3,203)
Marketable equity securities, fair value	41,556	56,638
Amortized Cost	1,692,456	1,850,507
Gross Unrealized Gains	37,913	12,559
Gross Unrealized Losses	(3,981)	(35,557)
Fair Value	1,726,388	1,827,509
Municipal bonds and obligations
Securities available for sale
Amortized Cost	104,325	109,648
Gross Unrealized Gains	5,813	2,272
Gross Unrealized Losses	0	(713)
Securities available for sale, at fair value	110,138	111,207
Securities held to maturity
Amortized Cost	252,936	264,524
Gross Unrealized Gains	13,095	3,569
Gross Unrealized Losses	(5)	(3,601)
Fair Value	266,026	264,492
Agency collateralized mortgage obligations
Securities available for sale
Amortized Cost	742,550	944,946
Gross Unrealized Gains	6,431	1,130
Gross Unrealized Losses	(169)	(15,192)
Securities available for sale, at fair value	748,812	930,884
Securities held to maturity
Amortized Cost	69,667	71,637
Gross Unrealized Gains	2,870	533
Gross Unrealized Losses	(50)	(778)
Fair Value	72,487	71,392
Agency mortgage-backed securities
Securities available for sale
Amortized Cost	146,589	175,406
Gross Unrealized Gains	1,515	36
Gross Unrealized Losses	(360)	(5,121)
Securities available for sale, at fair value	147,744	170,321
Securities held to maturity
Amortized Cost	6,271	7,219
Gross Unrealized Gains	29	0
Gross Unrealized Losses	0	(297)
Fair Value	6,300	6,922
Agency commercial mortgage-backed securities
Securities available for sale
Amortized Cost	148,066	62,200
Gross Unrealized Gains	176	0
Gross Unrealized Losses	(1,146)	(3,275)
Securities available for sale, at fair value	147,096	58,925
Securities held to maturity
Amortized Cost	10,353	10,417
Gross Unrealized Gains	51	0
Gross Unrealized Losses	0	(289)
Fair Value	10,404	10,128
Corporate bonds
Securities available for sale
Amortized Cost	115,395	120,718
Gross Unrealized Gains	1,788	593
Gross Unrealized Losses	(607)	(1,355)
Securities available for sale, at fair value	116,576	119,956
Tax advantaged economic development bonds
Securities held to maturity
Amortized Cost	18,456	19,718
Gross Unrealized Gains	218	22
Gross Unrealized Losses	(910)	(1,698)
Fair Value	17,764	18,042
Other bonds and obligations
Securities available for sale
Amortized Cost	40,414	8,355
Gross Unrealized Gains	780	34
Gross Unrealized Losses	(5)	(35)
Securities available for sale, at fair value	41,189	8,354
Securities held to maturity
Amortized Cost	296	248
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 296	$ 248

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