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Investment Securities (Investments Gross Unrealized Losses And Fair Value) (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | $ 149,462 | $ 319,678
Securities available for sale, Less than 12 months, Unrealized Losses | 4,202 | 2,618
Securities available for sale, 12 months or longer, Fair Value | 304,380 | 115,552
Securities available for sale, 12 months or longer, Unrealized Losses | 14,526 | 2,548
Securities available for sale, Fair Value, Total | 453,842 | 435,230
Securities available for sale, Unrealized Losses, Total | 18,728 | 5,166
Securities held to maturity, Less than 12 months, Fair Value | 142,317 | 113,419
Securities held to maturity, Less than 12 months, Unrealized Losses | 1,859 | 1,339
Securities held to maturity, 12 months or longer, Fair Value | 199,373 | 159,211
Securities held to maturity, 12 months or longer, Unrealized Losses | 10,565 | 4,485
Securities held to maturity, Fair Value, Total | 341,690 | 272,630
Securities held to maturity, Unrealized Losses, Total | 12,424 | 5,824
Total Securities, Less than 12 months, Fair Value | 291,779 | 433,097
Total Securities, Less than 12 months, Unrealized Losses | 6,061 | 3,957
Total Securities, 12 months or longer, Fair Value | 503,753 | 274,763
Total Securities, 12 months or longer, Unrealized Losses | 25,091 | 7,033
Total Securities, Fair Value | 795,532 | 707,860
Total Securities, Unrealized Losses | 31,152 | 10,990
U.S. Government Agencies And Government Sponsored Enterprises [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 88,647 | 95,046
Securities available for sale, Less than 12 months, Unrealized Losses | 2,621 | 571
Securities available for sale, 12 months or longer, Fair Value | 63,162 | 31,561
Securities available for sale, 12 months or longer, Unrealized Losses | 3,356 | 687
Securities available for sale, Fair Value, Total | 151,809 | 126,607
Securities available for sale, Unrealized Losses, Total | 5,977 | 1,258
State And Political Subdivisions [Member] |  |
Investment [Line Items] |  |
Securities held to maturity, Less than 12 months, Fair Value | 105,290 | 36,368
Securities held to maturity, Less than 12 months, Unrealized Losses | 858 | 295
Securities held to maturity, 12 months or longer, Fair Value | 28,646 | 14,492
Securities held to maturity, 12 months or longer, Unrealized Losses | 1,334 | 367
Securities held to maturity, Fair Value, Total | 133,936 | 50,860
Securities held to maturity, Unrealized Losses, Total | 2,192 | 662
Collateralized Mortgage Obligations [Member] | Federal National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities available for sale, 12 months or longer, Fair Value | 58 | 119
Securities available for sale, 12 months or longer, Unrealized Losses |  | 1
Securities available for sale, Fair Value, Total | 58 | 119
Securities available for sale, Unrealized Losses, Total |  | 1
Securities held to maturity, Less than 12 months, Fair Value | 1,982 | 16,830
Securities held to maturity, Less than 12 months, Unrealized Losses | 41 | 202
Securities held to maturity, 12 months or longer, Fair Value | 59,878 | 57,645
Securities held to maturity, 12 months or longer, Unrealized Losses | 3,229 | 1,756
Securities held to maturity, Fair Value, Total | 61,860 | 74,475
Securities held to maturity, Unrealized Losses, Total | 3,270 | 1,958
Collateralized Mortgage Obligations [Member] | Federal Home Loan Mortgage Corporation [Member] |  |
Investment [Line Items] |  |
Securities available for sale, 12 months or longer, Fair Value | 6 | 8
Securities available for sale, Fair Value, Total | 6 | 8
Securities held to maturity, Less than 12 months, Fair Value | 9,845 | 23,727
Securities held to maturity, Less than 12 months, Unrealized Losses | 390 | 337
Securities held to maturity, 12 months or longer, Fair Value | 67,728 | 66,467
Securities held to maturity, 12 months or longer, Unrealized Losses | 3,713 | 1,828
Securities held to maturity, Fair Value, Total | 77,573 | 90,194
Securities held to maturity, Unrealized Losses, Total | 4,103 | 2,165
Collateralized Mortgage Obligations [Member] | Government National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities held to maturity, Less than 12 months, Fair Value | 1,020 | 15,401
Securities held to maturity, Less than 12 months, Unrealized Losses | 15 | 340
Securities held to maturity, 12 months or longer, Fair Value | 16,937 | 5,635
Securities held to maturity, 12 months or longer, Unrealized Losses | 852 | 162
Securities held to maturity, Fair Value, Total | 17,957 | 21,036
Securities held to maturity, Unrealized Losses, Total | 867 | 502
Mortgage-Backed Securities [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 60,815 | 224,632
Securities available for sale, Less than 12 months, Unrealized Losses | 1,581 | 2,047
Securities available for sale, 12 months or longer, Fair Value | 241,218 | 83,991
Securities available for sale, 12 months or longer, Unrealized Losses | 11,170 | 1,861
Securities available for sale, Fair Value, Total | 302,033 | 308,623
Securities available for sale, Unrealized Losses, Total | 12,751 | 3,908
Securities held to maturity, Less than 12 months, Fair Value | 37,027 | 77,051
Securities held to maturity, Less than 12 months, Unrealized Losses | 1,001 | 1,044
Securities held to maturity, 12 months or longer, Fair Value | 170,727 | 144,719
Securities held to maturity, 12 months or longer, Unrealized Losses | 9,231 | 4,118
Securities held to maturity, Fair Value, Total | 207,754 | 221,770
Securities held to maturity, Unrealized Losses, Total | 10,232 | 5,162
Mortgage-Backed Securities [Member] | Federal National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 54,316 | 201,754
Securities available for sale, Less than 12 months, Unrealized Losses | 1,380 | 1,855
Securities available for sale, 12 months or longer, Fair Value | 208,371 | 67,383
Securities available for sale, 12 months or longer, Unrealized Losses | 9,398 | 1,365
Securities available for sale, Fair Value, Total | 262,687 | 269,137
Securities available for sale, Unrealized Losses, Total | 10,778 | 3,220
Securities held to maturity, Less than 12 months, Fair Value | 5,467 | 3,766
Securities held to maturity, Less than 12 months, Unrealized Losses | 151 | 29
Securities held to maturity, 12 months or longer, Fair Value | 6,098 | 2,694
Securities held to maturity, 12 months or longer, Unrealized Losses | 316 | 59
Securities held to maturity, Fair Value, Total | 11,565 | 6,460
Securities held to maturity, Unrealized Losses, Total | 467 | 88
Mortgage-Backed Securities [Member] | Federal Home Loan Mortgage Corporation [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 2,374 | 20,446
Securities available for sale, Less than 12 months, Unrealized Losses | 80 | 192
Securities available for sale, 12 months or longer, Fair Value | 32,041 | 15,601
Securities available for sale, 12 months or longer, Unrealized Losses | 1,767 | 483
Securities available for sale, Fair Value, Total | 34,415 | 36,047
Securities available for sale, Unrealized Losses, Total | 1,847 | 675
Securities held to maturity, Less than 12 months, Fair Value | 1,455 |
Securities held to maturity, Less than 12 months, Unrealized Losses | 30 |
Securities held to maturity, 12 months or longer, Fair Value | 2,889 | 3,094
Securities held to maturity, 12 months or longer, Unrealized Losses | 242 | 119
Securities held to maturity, Fair Value, Total | 4,344 | 3,094
Securities held to maturity, Unrealized Losses, Total | 272 | 119
Mortgage-Backed Securities [Member] | Government National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 4,125 | 2,432
Securities available for sale, Less than 12 months, Unrealized Losses | 121 |
Securities available for sale, 12 months or longer, Fair Value | 742 | 880
Securities available for sale, 12 months or longer, Unrealized Losses | 5 | 12
Securities available for sale, Fair Value, Total | 4,867 | 3,312
Securities available for sale, Unrealized Losses, Total | 126 | 12
Securities held to maturity, Less than 12 months, Fair Value | 17,258 | 17,327
Securities held to maturity, Less than 12 months, Unrealized Losses | 374 | 136
Securities held to maturity, 12 months or longer, Fair Value | 17,197 | 9,184
Securities held to maturity, 12 months or longer, Unrealized Losses | 879 | 194
Securities held to maturity, Fair Value, Total | 34,455 | 26,511
Securities held to maturity, Unrealized Losses, Total | $ 1,253 | $ 330

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