SECURITIES - Schedule of Unrealized Loss and Fair Value on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value
Less than 12 months	$ 249,413	$ 664,476
12 months or longer	374,649	198,397
Total	624,062	862,873
Unrealized Losses
Less than 12 months	(2,537)	(13,451)
12 months or longer	(7,279)	(4,992)
Total	(9,816)	(18,443)
Collateralized Loan Obligations [Member]
Fair Value
Less than 12 months	21,998	8,152
12 months or longer	0	51,694
Total	21,998	59,846
Unrealized Losses
Less than 12 months	(18)	(41)
12 months or longer	0	(938)
Total	(18)	(979)
Mortgage-backed securities of U.S. Government Sponsored Entities [Member]
Fair Value
Less than 12 months	152,796	327,759
12 months or longer	109,433	5,387
Total	262,229	333,146
Unrealized Losses
Less than 12 months	(1,963)	(5,991)
12 months or longer	(1,331)	(75)
Total	(3,294)	(6,066)
Collateralized Mortgage Obligations Of US Government Sponsored Entities [Member]
Fair Value
Less than 12 months	51,067	234,175
12 months or longer	225,546	58,912
Total	276,613	293,087
Unrealized Losses
Less than 12 months	(365)	(5,599)
12 months or longer	(5,142)	(2,096)
Total	(5,507)	(7,695)
Commercial mortgage backed securities of U.S. Government Sponsored Entities [Member]
Fair Value
Less than 12 months	3,111	7,934
12 months or longer	0	0
Total	3,111	7,934
Unrealized Losses
Less than 12 months	(10)	(102)
12 months or longer	0	0
Total	(10)	(102)
Private mortgage backed securities [Member]
Fair Value
Less than 12 months	0	0
12 months or longer	0	36,848
Total	0	36,848
Unrealized Losses
Less than 12 months	0	0
12 months or longer	0	(900)
Total	0	(900)
Private collateralized mortgage obligations [Member]
Fair Value
Less than 12 months	0	1,460
12 months or longer	22,003	38,417
Total	22,003	39,877
Unrealized Losses
Less than 12 months	0	0
12 months or longer	(358)	(816)
Total	(358)	(816)
Obligations of state and political subdivisions [Member]
Fair Value
Less than 12 months	11,556	39,321
12 months or longer	5,639	0
Total	17,195	39,321
Unrealized Losses
Less than 12 months	(86)	(895)
12 months or longer	(289)	0
Total	(375)	(895)
Corporate and other debt securities [member]
Fair Value
Less than 12 months	998	33,008
12 months or longer	8,301	0
Total	9,299	33,008
Unrealized Losses
Less than 12 months	0	(517)
12 months or longer	(89)	0
Total	(89)	(517)
Private commercial mortgage backed securities [Member]
Fair Value
Less than 12 months	7,887	12,667
12 months or longer	3,727	7,139
Total	11,614	19,806
Unrealized Losses
Less than 12 months	(95)	(306)
12 months or longer	(70)	(167)
Total	$ (165)	$ (473)