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Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015
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Schedule of Available-for-sale Securities [Line Items] |  |
Less than 12 Months Fair Value | $ 1,461,783 | $ 918,813
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | 25,415 | 9,247
12 Months or More Fair Value | 165,173 | 298,316
12 Months or More Unrealized Losses | (5,276) | (9,021)
Total Fair Value | 1,626,956 | 1,217,129
Total Unrealized Losses | (30,691) | (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] |  |
Less than 12 Months Fair Value | 1,029,116 | 664,509
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | 18,788 | 7,610
12 Months or More Fair Value | 159,046 | 214,325
12 Months or More Unrealized Losses | (4,930) | (7,381)
Total Fair Value | 1,188,162 | 878,834
Total Unrealized Losses | (23,718) | (14,991)
State and Municipal Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than 12 Months Fair Value | 211,342 | 48,261
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | 5,064 | 358
12 Months or More Fair Value | 3,384 | 31,383
12 Months or More Unrealized Losses | (133) | (580)
Total Fair Value | 214,726 | 79,644
Total Unrealized Losses | (5,197) | (938)
U.S. Government and Government-Sponsored Enterprise Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than 12 Months Fair Value | 218,811 | 193,400
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | 1,511 | 1,128
12 Months or More Fair Value | 0 | 40,034
12 Months or More Unrealized Losses | 0 | (718)
Total Fair Value | 218,811 | 233,434
Total Unrealized Losses | (1,511) | (1,846)
US Treasury Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than 12 Months Fair Value | 251 | 10,343
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | 1 | 136
12 Months or More Fair Value | 0 | 9,794
12 Months or More Unrealized Losses | 0 | (166)
Total Fair Value | 251 | 20,137
Total Unrealized Losses | (1) | (302)
Other Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than 12 Months Fair Value | 2,263 | 2,300
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | 51 | 15
12 Months or More Fair Value | 2,743 | 2,780
12 Months or More Unrealized Losses | (213) | (176)
Total Fair Value | 5,006 | 5,080
Total Unrealized Losses | $ (264) | $ (191)

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