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Investment Securities (Investments Gross Unrealized Losses And Fair Value) (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | $ 377,140 | $ 319,678
Securities available for sale, Less than 12 months, Unrealized Losses | 9,057 | 2,618
Securities available for sale, 12 months or longer, Fair Value | 112,573 | 115,552
Securities available for sale, 12 months or longer, Unrealized Losses | 4,110 | 2,548
Securities available for sale, Fair Value, Total | 489,713 | 435,230
Securities available for sale, Unrealized Losses, Total | 13,167 | 5,166
Securities held to maturity, Less than 12 months, Fair Value | 159,619 | 113,419
Securities held to maturity, Less than 12 months, Unrealized Losses | 3,127 | 1,339
Securities held to maturity, 12 months or longer, Fair Value | 156,102 | 159,211
Securities held to maturity, 12 months or longer, Unrealized Losses | 6,580 | 4,485
Securities held to maturity, Fair Value, Total | 315,721 | 272,630
Securities held to maturity, Unrealized Losses, Total | 9,707 | 5,824
Total Securities, Less than 12 months, Fair Value | 536,759 | 433,097
Total Securities, Less than 12 months, Unrealized Losses | 12,184 | 3,957
Total Securities, 12 months or longer, Fair Value | 268,675 | 274,763
Total Securities, 12 months or longer, Unrealized Losses | 10,690 | 7,033
Total Securities, Fair Value | 805,434 | 707,860
Total Securities, Unrealized Losses | 22,874 | 10,990
U.S. Government Agencies And Government Sponsored Enterprises [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 124,166 | 95,046
Securities available for sale, Less than 12 months, Unrealized Losses | 2,539 | 571
Securities available for sale, 12 months or longer, Fair Value | 30,944 | 31,561
Securities available for sale, 12 months or longer, Unrealized Losses | 1,273 | 687
Securities available for sale, Fair Value, Total | 155,110 | 126,607
Securities available for sale, Unrealized Losses, Total | 3,812 | 1,258
State And Political Subdivisions [Member] |  |
Investment [Line Items] |  |
Securities held to maturity, Less than 12 months, Fair Value | 86,593 | 36,368
Securities held to maturity, Less than 12 months, Unrealized Losses | 1,062 | 295
Securities held to maturity, 12 months or longer, Fair Value | 14,294 | 14,492
Securities held to maturity, 12 months or longer, Unrealized Losses | 659 | 367
Securities held to maturity, Fair Value, Total | 100,887 | 50,860
Securities held to maturity, Unrealized Losses, Total | 1,721 | 662
Collateralized Mortgage Obligations [Member] | Federal National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities available for sale, 12 months or longer, Fair Value | 95 | 119
Securities available for sale, 12 months or longer, Unrealized Losses |  | 1
Securities available for sale, Fair Value, Total | 95 | 119
Securities available for sale, Unrealized Losses, Total |  | 1
Securities held to maturity, Less than 12 months, Fair Value | 18,080 | 16,830
Securities held to maturity, Less than 12 months, Unrealized Losses | 426 | 202
Securities held to maturity, 12 months or longer, Fair Value | 51,855 | 57,645
Securities held to maturity, 12 months or longer, Unrealized Losses | 2,223 | 1,756
Securities held to maturity, Fair Value, Total | 69,935 | 74,475
Securities held to maturity, Unrealized Losses, Total | 2,649 | 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 | 7 | 8
Securities available for sale, Fair Value, Total | 7 | 8
Securities held to maturity, Less than 12 months, Fair Value | 21,491 | 23,727
Securities held to maturity, Less than 12 months, Unrealized Losses | 664 | 337
Securities held to maturity, 12 months or longer, Fair Value | 65,083 | 66,467
Securities held to maturity, 12 months or longer, Unrealized Losses | 2,633 | 1,828
Securities held to maturity, Fair Value, Total | 86,574 | 90,194
Securities held to maturity, Unrealized Losses, Total | 3,297 | 2,165
Collateralized Mortgage Obligations [Member] | Government National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities held to maturity, Less than 12 months, Fair Value | 11,448 | 15,401
Securities held to maturity, Less than 12 months, Unrealized Losses | 387 | 340
Securities held to maturity, 12 months or longer, Fair Value | 9,232 | 5,635
Securities held to maturity, 12 months or longer, Unrealized Losses | 331 | 162
Securities held to maturity, Fair Value, Total | 20,680 | 21,036
Securities held to maturity, Unrealized Losses, Total | 718 | 502
Mortgage-Backed Securities [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 252,974 | 224,632
Securities available for sale, Less than 12 months, Unrealized Losses | 6,518 | 2,047
Securities available for sale, 12 months or longer, Fair Value | 81,629 | 83,991
Securities available for sale, 12 months or longer, Unrealized Losses | 2,837 | 1,861
Securities available for sale, Fair Value, Total | 334,603 | 308,623
Securities available for sale, Unrealized Losses, Total | 9,355 | 3,908
Securities held to maturity, Less than 12 months, Fair Value | 73,026 | 77,051
Securities held to maturity, Less than 12 months, Unrealized Losses | 2,065 | 1,044
Securities held to maturity, 12 months or longer, Fair Value | 141,808 | 144,719
Securities held to maturity, 12 months or longer, Unrealized Losses | 5,921 | 4,118
Securities held to maturity, Fair Value, Total | 214,834 | 221,770
Securities held to maturity, Unrealized Losses, Total | 7,986 | 5,162
Mortgage-Backed Securities [Member] | Federal National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 226,028 | 201,754
Securities available for sale, Less than 12 months, Unrealized Losses | 5,855 | 1,855
Securities available for sale, 12 months or longer, Fair Value | 65,749 | 67,383
Securities available for sale, 12 months or longer, Unrealized Losses | 2,067 | 1,365
Securities available for sale, Fair Value, Total | 291,777 | 269,137
Securities available for sale, Unrealized Losses, Total | 7,922 | 3,220
Securities held to maturity, Less than 12 months, Fair Value | 6,604 | 3,766
Securities held to maturity, Less than 12 months, Unrealized Losses | 164 | 29
Securities held to maturity, 12 months or longer, Fair Value | 2,610 | 2,694
Securities held to maturity, 12 months or longer, Unrealized Losses | 125 | 59
Securities held to maturity, Fair Value, Total | 9,214 | 6,460
Securities held to maturity, Unrealized Losses, Total | 289 | 88
Mortgage-Backed Securities [Member] | Federal Home Loan Mortgage Corporation [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 22,258 | 20,446
Securities available for sale, Less than 12 months, Unrealized Losses | 597 | 192
Securities available for sale, 12 months or longer, Fair Value | 14,941 | 15,601
Securities available for sale, 12 months or longer, Unrealized Losses | 764 | 483
Securities available for sale, Fair Value, Total | 37,199 | 36,047
Securities available for sale, Unrealized Losses, Total | 1,361 | 675
Securities held to maturity, 12 months or longer, Fair Value | 3,000 | 3,094
Securities held to maturity, 12 months or longer, Unrealized Losses | 193 | 119
Securities held to maturity, Fair Value, Total | 3,000 | 3,094
Securities held to maturity, Unrealized Losses, Total | 193 | 119
Mortgage-Backed Securities [Member] | Government National Mortgage Association [Member] |  |
Investment [Line Items] |  |
Securities available for sale, Less than 12 months, Fair Value | 4,688 | 2,432
Securities available for sale, Less than 12 months, Unrealized Losses | 66 |
Securities available for sale, 12 months or longer, Fair Value | 837 | 880
Securities available for sale, 12 months or longer, Unrealized Losses | 6 | 12
Securities available for sale, Fair Value, Total | 5,525 | 3,312
Securities available for sale, Unrealized Losses, Total | 72 | 12
Securities held to maturity, Less than 12 months, Fair Value | 15,403 | 17,327
Securities held to maturity, Less than 12 months, Unrealized Losses | 424 | 136
Securities held to maturity, 12 months or longer, Fair Value | 10,028 | 9,184
Securities held to maturity, 12 months or longer, Unrealized Losses | 416 | 194
Securities held to maturity, Fair Value, Total | 25,431 | 26,511
Securities held to maturity, Unrealized Losses, Total | $ 840 | $ 330

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