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Investments - Investment Securities Continuous Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified | Jun. 30, 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 | $ 36,992 | $ 68,985
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than Twelve Months, Accumulated Loss | 122 | 1,188
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 3,222 | 2,227
Held-to-maturity Securities, Continuous Unrealized Loss Position Twelve Months Or Longer, Accumulated Loss | 122 | 150
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 40,214 | 71,212
Gross Unrealized Losses | 244 | 1,338
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 35,901 | 138,107
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 197 | 6,191
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 20,717 | 7,525
Gross Unrealized Losses, 12 Months or Greater | 3,856 | 2,844
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 56,618 | 145,632
Available-for Sale, Gross Unrealized Losses, Total | 4,053 | 9,035
Corporate bonds [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 19,268 | 14,090
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than Twelve Months, Accumulated Loss | 57 | 41
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 19,268 | 14,090
Gross Unrealized Losses | 57 | 41
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 20,127 | 29,691
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 30 | 361
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 986 |
Gross Unrealized Losses, 12 Months or Greater | 3 |
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 21,113 | 29,691
Available-for Sale, Gross Unrealized Losses, Total | 33 | 361
States and political subdivisions [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 14,872 | 54,895
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than Twelve Months, Accumulated Loss | 64 | 1,147
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 1,423 | 311
Held-to-maturity Securities, Continuous Unrealized Loss Position Twelve Months Or Longer, Accumulated Loss | 2 | 6
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 16,295 | 55,206
Gross Unrealized Losses | 66 | 1,153
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 14,689 | 101,908
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 82 | 4,798
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 12,700 | 1,753
Gross Unrealized Losses, 12 Months or Greater | 1,677 | 342
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 27,389 | 103,661
Available-for Sale, Gross Unrealized Losses, Total | 1,759 | 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 | 605 | 1,303
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 79 | 465
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 7,031 | 5,772
Gross Unrealized Losses, 12 Months or Greater | 2,176 | 2,502
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total | 7,636 | 7,075
Available-for Sale, Gross Unrealized Losses, Total | 2,255 | 2,967
Equity securities [Member] |  |
Investment [Line Items] |  |
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months | 480 | 5,205
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months | 6 | 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 | 480 | 5,205
Available-for Sale, Gross Unrealized Losses, Total | 6 | 567
Asset-backed securities [Member] |  |
Investment [Line Items] |  |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 1,799 | 1,916
Held-to-maturity Securities, Continuous Unrealized Loss Position Twelve Months Or Longer, Accumulated Loss | 120 | 144
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 1,799 | 1,916
Gross Unrealized Losses | 120 | 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 | 2,852 |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than Twelve Months, Accumulated Loss | 1 |
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value | 2,852 |
Gross Unrealized Losses | 1 |
Held-to-maturity securities [Member] |  |
Investment [Line Items] |  |
Fair Value of Investments with Unrealized Losses, Less Than 12 months | 72,893 | 207,092
Gross Unrealized Loss, Less Than 12 Months | 319 | 7,379
Fair Value of Investments with Unrealized Losses, 12 Months or Greater | 23,939 | 9,752
Gross Unrealized Losses, 12 Months or Greater | 3,978 | 2,994
Fair Value of Investments with Unrealized Losses, Total | 96,832 | 216,844
Gross Unrealized Losses, Total | $ 4,297 | $ 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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