Securities - Summary of Securities with Unrealized Losses, Segregated by Duration of Unrealized Loss (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available for Sale
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 189,005	$ 210,274
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	352	902
Available-for-sale Securities, 12 Months or Longer, Fair Value	21,163	14,956
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	582	218
Available-for-sale Securities, Fair Value, Total	210,168	225,230
Available-for-sale Securities, Unrealized Losses, Total	934	1,120
Held for Investment
Held-to-maturity Securities, Less than 12 Months, Fair Value	21
Held-to-maturity Securities, Fair Value, Total	21
U.S. Treasuries [Member]
Available for Sale
Available-for-sale Securities, Less than 12 Months, Fair Value	139,762	149,589
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	45	178
Available-for-sale Securities, Fair Value, Total	139,762	149,589
Available-for-sale Securities, Unrealized Losses, Total	45	178
U.S. Federal Agencies [Member]
Available for Sale
Available-for-sale Securities, Less than 12 Months, Fair Value	46,948	40,551
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	118	113
Available-for-sale Securities, 12 Months or Longer, Fair Value	5,969	13,653
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	35	62
Available-for-sale Securities, Fair Value, Total	52,917	54,204
Available-for-sale Securities, Unrealized Losses, Total	153	175
Mortgage Backed Securities [Member]
Available for Sale
Available-for-sale Securities, Less than 12 Months, Fair Value	59	17,041
Available-for-sale Securities, Less than 12 Months, Unrealized Losses		585
Available-for-sale Securities, 12 Months or Longer, Fair Value	14,844	26
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	543	1
Available-for-sale Securities, Fair Value, Total	14,903	17,067
Available-for-sale Securities, Unrealized Losses, Total	543	586
Held for Investment
Held-to-maturity Securities, Less than 12 Months, Fair Value	21
Held-to-maturity Securities, Fair Value, Total	21
States and Political Subdivisions [Member]
Available for Sale
Available-for-sale Securities, Less than 12 Months, Fair Value	1,932	3,093
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	47	26
Available-for-sale Securities, 12 Months or Longer, Fair Value	245	977
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	1	23
Available-for-sale Securities, Fair Value, Total	2,177	4,070
Available-for-sale Securities, Unrealized Losses, Total	48	49
Other Securities [Member]
Available for Sale
Available-for-sale Securities, Less than 12 Months, Fair Value	304
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	142
Available-for-sale Securities, 12 Months or Longer, Fair Value	105	300
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	3	132
Available-for-sale Securities, Fair Value, Total	409	300
Available-for-sale Securities, Unrealized Losses, Total	$ 145	$ 132

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

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