Debt and Equity Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Detail) (USD $) | Sep. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | Security | Security |
Held To Maturity Debt Securities [Line Items] | ' | ' |
Held to Maturity Securities, Fair Value, Less than 12 Month | $1,111 | $14,495 |
Held to Maturity Securities, Unrealized losses, Less than 12 Month | 4 | 751 |
Held to Maturity Securities, Number of securities included, Less than 12 Month | 3 | 26 |
Held to Maturity Securities, Fair Value, 12 Month or More | 10,958 | 343 |
Held to Maturity Securities, Unrealized losses, 12 Month or More | 384 | 8 |
Held to Maturity Securities, Number of securities included, 12 Month or More | 16 | 2 |
Held to Maturity Securities, Total Fair Value | 12,069 | 14,838 |
Held to Maturity Securities, Total Unrealized Losses | 388 | 759 |
Available-for-Sale Securities, Fair Value, Less than 12 Month | 158,820 | 211,684 |
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month | 1,463 | 5,902 |
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | 65 | 83 |
Available-for-Sale Securities, Fair Value, 12 Month or More | 112,914 | 26,111 |
Available-for-Sale Securities, Unrealized Loss, 12 Month or More | 3,052 | 1,949 |
Available-for-Sale Securities, Number of securities included, 12 Month or More | 57 | 23 |
Available-for-Sale Securities, Total Fair Value | 271,734 | 237,795 |
Available-for-Sale Securities, Total Unrealized Losses | 4,515 | 7,851 |
US Government-Sponsored Enterprises (GSEs) [Member] | ' | ' |
Held To Maturity Debt Securities [Line Items] | ' | ' |
Available-for-Sale Securities, Fair Value, Less than 12 Month | 44,030 | 103,502 |
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month | 343 | 4,289 |
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | 15 | 32 |
Available-for-Sale Securities, Fair Value, 12 Month or More | 85,021 | 19,479 |
Available-for-Sale Securities, Unrealized Loss, 12 Month or More | 2,412 | 1,603 |
Available-for-Sale Securities, Number of securities included, 12 Month or More | 28 | 7 |
Available-for-Sale Securities, Total Fair Value | 129,051 | 122,981 |
Available-for-Sale Securities, Total Unrealized Losses | 2,755 | 5,892 |
Government- Sponsored Enterprises (GSEs) Residential Mortgage Backed [Member] | ' | ' |
Held To Maturity Debt Securities [Line Items] | ' | ' |
Held to Maturity Securities, Fair Value, Less than 12 Month | ' | 6,678 |
Held to Maturity Securities, Unrealized losses, Less than 12 Month | ' | 520 |
Held to Maturity Securities, Number of securities included, Less than 12 Month | ' | 5 |
Held to Maturity Securities, Fair Value, 12 Month or More | 6,775 | ' |
Held to Maturity Securities, Unrealized losses, 12 Month or More | 310 | ' |
Held to Maturity Securities, Number of securities included, 12 Month or More | 6 | ' |
Held to Maturity Securities, Total Fair Value | 6,775 | 6,678 |
Held to Maturity Securities, Total Unrealized Losses | 310 | 520 |
Available-for-Sale Securities, Fair Value, Less than 12 Month | 92,184 | 97,805 |
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month | 847 | 1,449 |
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | 35 | 32 |
Available-for-Sale Securities, Fair Value, 12 Month or More | 22,462 | 1,866 |
Available-for-Sale Securities, Unrealized Loss, 12 Month or More | 461 | 32 |
Available-for-Sale Securities, Number of securities included, 12 Month or More | 14 | 2 |
Available-for-Sale Securities, Total Fair Value | 114,646 | 99,671 |
Available-for-Sale Securities, Total Unrealized Losses | 1,308 | 1,481 |
Obligations of States and Political Subdivisions [Member] | ' | ' |
Held To Maturity Debt Securities [Line Items] | ' | ' |
Held to Maturity Securities, Fair Value, Less than 12 Month | 1,111 | 7,817 |
Held to Maturity Securities, Unrealized losses, Less than 12 Month | 4 | 231 |
Held to Maturity Securities, Number of securities included, Less than 12 Month | 3 | 21 |
Held to Maturity Securities, Fair Value, 12 Month or More | 4,183 | 343 |
Held to Maturity Securities, Unrealized losses, 12 Month or More | 74 | 8 |
Held to Maturity Securities, Number of securities included, 12 Month or More | 10 | 2 |
Held to Maturity Securities, Total Fair Value | 5,294 | 8,160 |
Held to Maturity Securities, Total Unrealized Losses | 78 | 239 |
Available-for-Sale Securities, Fair Value, Less than 12 Month | 1,602 | 5,645 |
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month | 7 | 95 |
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | 3 | 14 |
Available-for-Sale Securities, Fair Value, 12 Month or More | 5,431 | 4,766 |
Available-for-Sale Securities, Unrealized Loss, 12 Month or More | 179 | 314 |
Available-for-Sale Securities, Number of securities included, 12 Month or More | 15 | 14 |
Available-for-Sale Securities, Total Fair Value | 7,033 | 10,411 |
Available-for-Sale Securities, Total Unrealized Losses | 186 | 409 |
SBAP Member | ' | ' |
Held To Maturity Debt Securities [Line Items] | ' | ' |
Available-for-Sale Securities, Fair Value, Less than 12 Month | 21,004 | 4,732 |
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month | 266 | 69 |
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | 12 | 5 |
Available-for-Sale Securities, Fair Value, 12 Month or More | ' | ' |
Available-for-Sale Securities, Unrealized Loss, 12 Month or More | ' | ' |
Available-for-Sale Securities, Number of securities included, 12 Month or More | ' | ' |
Available-for-Sale Securities, Total Fair Value | 21,004 | 4,732 |
Available-for-Sale Securities, Total Unrealized Losses | $266 | $69 |