Investment Securities (Detail) - Gross unrealized losses on investment securities and the fair value of the related securities (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Securities available for sale
Number Of Securities Less than 12 Months	7	7
Fair Value Less than 12 Months	$ 33,588	$ 46,957
Unrealized Losses Less than 12 Months	341	244
Number Of Securities 12 Months or Longer	38	40
Fair Value 12 Months or Longer	87,523	93,198
Unrealized Losses 12 Months or Longer	5,183	7,063
Number Of Securities Total	45	47
Fair Value Total	121,111	140,155
Unrealized Losses Total	5,524	7,307
State And Municipal Obligations [Member]
Securities available for sale
Number Of Securities Less than 12 Months	3	2
Fair Value Less than 12 Months	6,767	6,038
Unrealized Losses Less than 12 Months	150	61
Number Of Securities 12 Months or Longer	0	0
Fair Value 12 Months or Longer	0	0
Unrealized Losses 12 Months or Longer	0	0
Number Of Securities Total	3	2
Fair Value Total	6,767	6,038
Unrealized Losses Total	150	61
Collateralized Debt Obligations [Member]
Securities available for sale
Number Of Securities Less than 12 Months	0	0
Fair Value Less than 12 Months	0	0
Unrealized Losses Less than 12 Months	0	0
Number Of Securities 12 Months or Longer	12	12
Fair Value 12 Months or Longer	3,004	2,744
Unrealized Losses 12 Months or Longer	2,678	3,015
Number Of Securities Total	12	12
Fair Value Total	3,004	2,744
Unrealized Losses Total	2,678	3,015
Mortgage Backed Securities Excluding Collateralized Mortgage Obligations [Member]
Securities available for sale
Number Of Securities Less than 12 Months	3	3
Fair Value Less than 12 Months	25,950	26,186
Unrealized Losses Less than 12 Months	191	150
Number Of Securities 12 Months or Longer	0	1
Fair Value 12 Months or Longer	0	454
Unrealized Losses 12 Months or Longer	0	1
Number Of Securities Total	3	4
Fair Value Total	25,950	26,640
Unrealized Losses Total	191	151
Collateralized Mortgage Obligations [Member]
Securities available for sale
Number Of Securities Less than 12 Months	1	2
Fair Value Less than 12 Months	871	14,733
Unrealized Losses Less than 12 Months	0	33
Number Of Securities 12 Months or Longer	25	25
Fair Value 12 Months or Longer	83,689	88,185
Unrealized Losses 12 Months or Longer	2,339	3,867
Number Of Securities Total	26	27
Fair Value Total	84,560	102,918
Unrealized Losses Total	2,339	3,900
Other Securities [Member]
Securities available for sale
Number Of Securities Less than 12 Months	0	0
Fair Value Less than 12 Months	0	0
Unrealized Losses Less than 12 Months	0	0
Number Of Securities 12 Months or Longer	1	2
Fair Value 12 Months or Longer	830	1,815
Unrealized Losses 12 Months or Longer	166	180
Number Of Securities Total	1	2
Fair Value Total	830	1,815
Unrealized Losses Total	$ 166	$ 180