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Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) - USD ($) $ in Thousands | Mar. 31, 2017 | Dec. 31, 2016
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Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | $ 11,017 | $ 10,231
Less than 12 Months Fair Value | 1,398,191 | 1,461,783
Less than 12 Months Unrealized Losses | (22,701) | (25,415)
12 Months or More Fair Value | 161,992 | 165,173
12 Months or More Unrealized Losses | (6,106) | (5,276)
Total Fair Value | 1,560,183 | 1,626,956
Total Unrealized Losses | (28,807) | (30,691)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 28,807 | 30,691
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 2,400 | 2,760
Less than 12 Months Fair Value | 1,038,971 | 1,029,116
Less than 12 Months Unrealized Losses | (17,020) | (18,788)
12 Months or More Fair Value | 155,846 | 159,046
12 Months or More Unrealized Losses | (5,796) | (4,930)
Total Fair Value | 1,194,817 | 1,188,162
Total Unrealized Losses | (22,816) | (23,718)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 22,816 | 23,718
State and Municipal Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 7,316 | 6,343
Less than 12 Months Fair Value | 162,860 | 211,342
Less than 12 Months Unrealized Losses | (4,249) | (5,064)
12 Months or More Fair Value | 3,412 | 3,384
12 Months or More Unrealized Losses | (88) | (133)
Total Fair Value | 166,272 | 214,726
Total Unrealized Losses | (4,337) | (5,197)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 4,337 | 5,197
US Government Corporations and Agencies Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 1,241 | 1,065
Less than 12 Months Fair Value | 193,846 | 218,811
Less than 12 Months Unrealized Losses | (1,381) | (1,511)
12 Months or More Fair Value | 0 | 0
12 Months or More Unrealized Losses | 0 | 0
Total Fair Value | 193,846 | 218,811
Total Unrealized Losses | (1,381) | (1,511)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 1,381 | 1,511
US Government Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 0 | 0
Less than 12 Months Fair Value | 251 | 251
Less than 12 Months Unrealized Losses | 0 | (1)
12 Months or More Fair Value | 0 | 0
12 Months or More Unrealized Losses | 0 | 0
Total Fair Value | 251 | 251
Total Unrealized Losses | 0 | (1)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 1
Other Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 60 | 63
Less than 12 Months Fair Value | 2,263 | 2,263
Less than 12 Months Unrealized Losses | (51) | (51)
12 Months or More Fair Value | 2,734 | 2,743
12 Months or More Unrealized Losses | (222) | (213)
Total Fair Value | 4,997 | 5,006
Total Unrealized Losses | (273) | (264)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | $ 273 | $ 264

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