SECURITIES - Amortized Cost and Fair Value of Securities Available for Sale and Held for Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	$ 1,018,297	$ 960,809
Gross Unrealized Gains, Available for Sale	6,408	3,767
Gross Unrealized Losses, Available for Sale	(7,961)	(14,073)
Fair Value, Available for Sale	1,016,744	950,503
Gross Amortized Cost, Held for Investment Securities	397,096	372,498
Gross Unrealized Gains, Held for Investment Securities	2,845	1,753
Gross Unrealized Losses, Held for Investment Securities	(2,584)	(4,370)
Fair Value, Held for Investment Securities	397,357	369,881
U.S. Treasury Securities and obligations of U.S. Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	10,907	12,073
Gross Unrealized Gains, Available for Sale	300	255
Gross Unrealized Losses, Available for Sale	0	0
Fair Value, Available for Sale	11,207	12,328
Mortgage-backed securities of U.S. Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	291,482	287,726
Gross Unrealized Gains, Available for Sale	1,250	585
Gross Unrealized Losses, Available for Sale	(2,632)	(4,823)
Fair Value, Available for Sale	290,100	283,488
Gross Amortized Cost, Held for Investment Securities	183,877	159,941
Gross Unrealized Gains, Held for Investment Securities	1,413	704
Gross Unrealized Losses, Held for Investment Securities	(959)	(1,243)
Fair Value, Held for Investment Securities	184,331	159,402
Collateralized Mortgage Obligations Of US Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	217,634	238,805
Gross Unrealized Gains, Available for Sale	614	314
Gross Unrealized Losses, Available for Sale	(3,951)	(5,065)
Fair Value, Available for Sale	214,297	234,054
Gross Amortized Cost, Held for Investment Securities	135,596	147,208
Gross Unrealized Gains, Held for Investment Securities	461	386
Gross Unrealized Losses, Held for Investment Securities	(1,564)	(2,630)
Fair Value, Held for Investment Securities	134,493	144,964
Commercial mortgage backed securities of U.S. Government Sponsored Entities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	22,304	22,351
Gross Unrealized Gains, Available for Sale	506	222
Gross Unrealized Losses, Available for Sale	(9)	(28)
Fair Value, Available for Sale	22,801	22,545
Gross Amortized Cost, Held for Investment Securities	17,420	17,375
Gross Unrealized Gains, Held for Investment Securities	585	233
Gross Unrealized Losses, Held for Investment Securities	0	(74)
Fair Value, Held for Investment Securities	18,005	17,534
Private mortgage backed securities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	32,860	32,780
Gross Unrealized Gains, Available for Sale	864	0
Gross Unrealized Losses, Available for Sale	(92)	(791)
Fair Value, Available for Sale	33,632	31,989
Fair Value, Held for Investment Securities	0
Private collateralized mortgage obligations [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	55,828	67,542
Gross Unrealized Gains, Available for Sale	616	563
Gross Unrealized Losses, Available for Sale	(488)	(816)
Fair Value, Available for Sale	55,956	67,289
Gross Amortized Cost, Held for Investment Securities	5,878	6,427
Gross Unrealized Gains, Held for Investment Securities	8	0
Gross Unrealized Losses, Held for Investment Securities	(61)	(109)
Fair Value, Held for Investment Securities	5,825	6,318
Collateralized loan obligations [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	222,725	124,716
Gross Unrealized Gains, Available for Sale	455	838
Gross Unrealized Losses, Available for Sale	(41)	(665)
Fair Value, Available for Sale	223,139	124,889
Gross Amortized Cost, Held for Investment Securities	54,325	41,547
Gross Unrealized Gains, Held for Investment Securities	378	430
Gross Unrealized Losses, Held for Investment Securities	0	(314)
Fair Value, Held for Investment Securities	54,703	41,663
Obligations of state and political subdivisions [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	62,847	63,161
Gross Unrealized Gains, Available for Sale	938	622
Gross Unrealized Losses, Available for Sale	(385)	(895)
Fair Value, Available for Sale	63,400	62,888
Corporate and other debt securities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	70,930	74,121
Gross Unrealized Gains, Available for Sale	676	257
Gross Unrealized Losses, Available for Sale	(168)	(517)
Fair Value, Available for Sale	71,438	73,861
Fair Value, Held for Investment Securities	0
Private commercial mortgage backed securities [Member]
Amortized cost and fair value of securities available for sale and held for investment
Gross Amortized Cost, Available for Sale	30,780	37,534
Gross Unrealized Gains, Available for Sale	189	111
Gross Unrealized Losses, Available for Sale	(195)	(473)
Fair Value, Available for Sale	30,774	$ 37,172
Fair Value, Held for Investment Securities	$ 0