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Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
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Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | $ 509,631 | $ 536,409
Gross Unrealized Gains | 6,817 | 9,916
Gross Unrealized Losses | (807) | (199)
Estimated Fair Value, Total | 515,641 | 546,126
U.S. treasuries [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 29,946 |
Gross Unrealized Gains |  |
Gross Unrealized Losses | (85) |
Estimated Fair Value, Total | 29,861 |
U.S. Federal agencies [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 386,391 | 452,554
Gross Unrealized Gains | 1,399 | 3,654
Gross Unrealized Losses | (505) | (164)
Estimated Fair Value, Total | 387,285 | 456,044
Mortgage backed securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 32,057 | 19,100
Gross Unrealized Gains | 625 | 825
Gross Unrealized Losses | (4) | (1)
Estimated Fair Value, Total | 32,678 | 19,924
States and political subdivisions [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 49,116 | 53,912
Gross Unrealized Gains | 1,290 | 2,875
Gross Unrealized Losses | (72) | (20)
Estimated Fair Value, Total | 50,334 | 56,767
Other securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 12,121 | 10,843
Gross Unrealized Gains | 3,503 | 2,562
Gross Unrealized Losses | (141) | (14)
Estimated Fair Value, Total | $ 15,483 | $ 13,391

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- Definition Amount of accumulated pre-tax unrealized gain before deducting pre-tax unrealized losses on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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- Definition Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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