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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, 2016 | Dec. 31, 2015
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Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | $ 33,588 | $ 18,352
Less than 12 Months Fair Value | 125,078 | 918,813
Less than 12 Months Unrealized Losses | (658) | (9,247)
12 Months or More Fair Value | 213,295 | 298,316
12 Months or More Unrealized Losses | (3,763) | (9,021)
Total Fair Value | 338,373 | 1,217,129
Total Unrealized Losses | (4,421) | (18,268)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 4,421 | 18,268
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 | 14,247 | 4,525
Less than 12 Months Fair Value | 95,313 | 664,509
Less than 12 Months Unrealized Losses | (533) | (7,610)
12 Months or More Fair Value | 190,975 | 214,325
12 Months or More Unrealized Losses | (3,328) | (7,381)
Total Fair Value | 286,288 | 878,834
Total Unrealized Losses | (3,861) | (14,991)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 3,861 | 14,991
State and Municipal Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 14,257 | 12,690
Less than 12 Months Fair Value | 25,702 | 48,261
Less than 12 Months Unrealized Losses | (125) | (358)
12 Months or More Fair Value | 19,010 | 31,383
12 Months or More Unrealized Losses | (289) | (580)
Total Fair Value | 44,712 | 79,644
Total Unrealized Losses | (414) | (938)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 414 | 938
US Government Corporations and Agencies Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 5,031 | 1,113
Less than 12 Months Fair Value | 4,063 | 193,400
Less than 12 Months Unrealized Losses | 0 | (1,128)
12 Months or More Fair Value | 500 | 40,034
12 Months or More Unrealized Losses | 0 | (718)
Total Fair Value | 4,563 | 233,434
Total Unrealized Losses | 0 | (1,846)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 1,846
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 |  | 10,343
Less than 12 Months Unrealized Losses |  | (136)
12 Months or More Fair Value |  | 9,794
12 Months or More Unrealized Losses |  | (166)
Total Fair Value |  | 20,137
Total Unrealized Losses |  | (302)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 302
Other Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale Debt Securities Gross Unrealized Gain, instant | 53 | 24
Less than 12 Months Fair Value | 0 | 2,300
Less than 12 Months Unrealized Losses | 0 | (15)
12 Months or More Fair Value | 2,810 | 2,780
12 Months or More Unrealized Losses | (146) | (176)
Total Fair Value | 2,810 | 5,080
Total Unrealized Losses | (146) | (191)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | $ 146 | $ 191

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