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Investments - Investment Securities Continuous Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2014 | Dec. 31, 2013
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Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | $ 54,704 | $ 68,985
Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Accumulated Loss | 342 | 1,188
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 3,878 | 2,227
Held To Maturity Securities, Continuous Unrealized Loss Position Twelve Months Or Longer Accumulated Loss | 174 | 150
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 58,582 | 71,212
Gross Unrealized Losses | 516 | 1,338
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 90,883 | 138,107
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 2,018 | 6,191
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 17,942 | 7,525
Gross Unrealized Losses, 12 Months or Greater | 3,987 | 2,844
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 108,825 | 145,632
Available-for Sale, Gross Unrealized Losses, Total | 6,005 | 9,035
Corporate bonds [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 24,290 | 14,090
Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Accumulated Loss | 74 | 41
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 24,290 | 14,090
Gross Unrealized Losses | 74 | 41
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 45,493 | 29,691
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 198 | 361
Fair Value of Investments with Unrealized Losses, 12 Months or Greater |  |
Gross Unrealized Losses, 12 Months or Greater |  |
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 45,493 | 29,691
Available-for Sale, Gross Unrealized Losses, Total | 198 | 361
States and political subdivisions [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 27,027 | 54,895
Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Accumulated Loss | 262 | 1,147
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 2,012 | 311
Held To Maturity Securities, Continuous Unrealized Loss Position Twelve Months Or Longer Accumulated Loss | 41 | 6
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 29,039 | 55,206
Gross Unrealized Losses | 303 | 1,153
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 43,605 | 101,908
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 1,371 | 4,798
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 12,247 | 1,753
Gross Unrealized Losses, 12 Months or Greater | 1,419 | 342
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 55,852 | 103,661
Available-for Sale, Gross Unrealized Losses, Total | 2,790 | 5,140
U.S. agency-based mortgage-backed securities [Member] |  |
Investment [Line Items] |  |
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 1,324 | 1,303
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 423 | 465
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 5,695 | 5,772
Gross Unrealized Losses, 12 Months or Greater | 2,568 | 2,502
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 7,019 | 7,075
Available-for Sale, Gross Unrealized Losses, Total | 2,991 | 2,967
Equity securities [Member] |  |
Investment [Line Items] |  |
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 461 | 5,205
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 26 | 567
Fair Value of Investments with Unrealized Losses, 12 Months or Greater |  |
Gross Unrealized Losses, 12 Months or Greater |  |
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 461 | 5,205
Available-for Sale, Gross Unrealized Losses, Total | 26 | 567
Asset-backed securities [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 1,866 | 1,916
Held To Maturity Securities, Continuous Unrealized Loss Position Twelve Months Or Longer Accumulated Loss | 133 | 144
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 1,866 | 1,916
Gross Unrealized Losses | 133 | 144
U.S. Treasury securities and obligations of U.S. government agencies [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 3,387 |
Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Accumulated Loss | 6 |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 3,387 |
Gross Unrealized Losses | 6 |
Held-to-maturity securities [Member] |  |
Investment [Line Items] |  |
Fair Value of Investments with Unrealized Losses, Less Than 12 months | 145,587 | 207,092
Gross Unrealized Loss, Less Than 12 Months | 2,360 | 7,379
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 21,820 | 9,752
Gross Unrealized Losses, 12 Months or Greater | 4,161 | 2,994
Fair Value of Investments with Unrealized Losses, Total | 167,407 | 216,844
Gross Unrealized Losses, Total | $ 6,521 | $ 10,373

X
- Definition Amount of accumulated pre-tax unrealized loss on securities classified as available-for-sale impacting investments. + References No definition available. + Details
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- Definition Amount of accumulated pre-tax unrealized loss on investments in available-for-sale securities that have been in a loss position for less than twelve months impacting investments. + References No definition available. + Details
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- Definition This item represents the excess of amortized cost basis over fair value of securities in a loss position and which are categorized as held-to-maturity. + References No definition available. + Details
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- Definition This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for less than twelve months for those securities which are categorized as held-to-maturity. + References No definition available. + Details
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- Definition Amount of accumulated pre-tax unrealized loss on investments in held-to-maturity securities that have been in a loss position for twelve months or longer. + References No definition available. + Details
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- Definition This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 + Details
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