SECURITIES (Temporarily Impaired Available-For-Sale Securities With Continuous Unrealized Loss Positions) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 1,156,017	$ 1,330,910
12 Months or Longer, Fair Value	412,219	29,760
Total, Fair Value	1,568,236	1,360,670
Less Than 12 Months, Unrealized Losses	4,283	11,083
12 Months or Longer, Unrealized Losses	6,306	240
Total, Unrealized Losses	10,589	11,323
US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	1,013,354	1,082,573
12 Months or Longer, Fair Value	335,579
Total, Fair Value	1,348,933	1,082,573
Less Than 12 Months, Unrealized Losses	3,213	6,065
12 Months or Longer, Unrealized Losses	2,971
Total, Unrealized Losses	6,184	6,065
U.S. Government Agency Issued Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	45,264	71,599
12 Months or Longer, Fair Value	34,636	15,375
Total, Fair Value	79,900	86,974
Less Than 12 Months, Unrealized Losses	365	1,783
12 Months or Longer, Unrealized Losses	900	115
Total, Unrealized Losses	1,265	1,898
U.S. Government Agency Issued Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	89,351	129,940
12 Months or Longer, Fair Value	34,176	14,385
Total, Fair Value	123,527	144,325
Less Than 12 Months, Unrealized Losses	684	1,084
12 Months or Longer, Unrealized Losses	364	125
Total, Unrealized Losses	1,048	1,209
Obligations Of States And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	8,048	46,798
12 Months or Longer, Fair Value	7,828
Total, Fair Value	15,876	46,798
Less Than 12 Months, Unrealized Losses	21	2,151
12 Months or Longer, Unrealized Losses	2,071
Total, Unrealized Losses	$ 2,092	$ 2,151