INVESTMENT SECURITIES (Amortized Cost and Estimated Fair Value of Investment Securities) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Held to Maturity, Amortized Cost
Mortgage-backed securities			$ 217,668
Held to Maturity, Estimated Fair Value
Mortgage-backed securities			214,366
Available for Sale, Amortized Cost
Due in one year or less			6,701
Due after one year through five years			132,559
Due after five years through ten years			67,541
Due after ten years			76,631
Mortgage-backed securities			962,732
Other			564
Total			1,246,728
Available for Sale, Estimated Fair Value
Due in one year or less			6,699
Due after one year through five years			133,374
Due after five years through ten years			67,664
Due after ten years			76,693
Mortgage-backed securities			958,757
Other			660
Total			1,243,847	$ 1,272,255
Available for sale
Gross proceeds from sale of available for sale investment securities	$ 119,400	$ 162,500	0	117,496	$ 162,470
Purchases of investment securities available for sale	$ 120,600		195,456	344,766	$ 98,408
Gross realized gains on the sales of the available for sale investment securities		900
Gross realized losses on the sales of the available for sale investment securities		$ 700
Average net yield of available for sale mortgage backed securities sold	1.35%	2.69%
Weighted average life of available for sale mortgage backed securities sold	4 years 4 months 24 days	5 years 8 months 12 days
Net realized gains on the sales of the available for sale investment securities	$ 1,900
Investment securities pledged to party with no right to sell or repledge the collateral			$ 1,100,000	$ 1,002,400
Non Agency Commercial Mortgage Backed Securities and Corporate Bond Securities
Available for sale
Average net yield of available for sale mortgage backed securities sold	2.71%
Weighted average life of available for sale mortgage backed securities sold	7 years 7 months 6 days