Investment Securities (Detail) - Gross unrealized losses on investment securities and the fair value of the related securities (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2011
Number Of Securities Less than 12 Months	7	19	8
Fair Value Less than 12 Months	$ 46,957	$ 90,910	$ 41,485
Unrealized Losses Less than 12 Months	244	3,435	655
Number Of Securities 12 Months or Longer	40	30	30
Fair Value 12 Months or Longer	93,198	38,559	41,404
Unrealized Losses 12 Months or Longer	7,063	6,804	5,825
Number Of Securities Total	47	49	38
Fair Value Total	140,155	129,469	82,889
Unrealized Losses Total	7,307	10,239	6,480
State And Municipal Obligations [Member]
Number Of Securities Less than 12 Months	2
Fair Value Less than 12 Months	6,038
Unrealized Losses Less than 12 Months	61
Number Of Securities 12 Months or Longer	0
Fair Value 12 Months or Longer	0
Unrealized Losses 12 Months or Longer	0
Number Of Securities Total	2
Fair Value Total	6,038
Unrealized Losses Total	61
Collateralized Debt Obligations [Member]
Number Of Securities Less than 12 Months	0	1	1
Fair Value Less than 12 Months	0	260	256
Unrealized Losses Less than 12 Months	0	47	50
Number Of Securities 12 Months or Longer	12	14	14
Fair Value 12 Months or Longer	2,744	2,987	2,818
Unrealized Losses 12 Months or Longer	3,015	3,718	4,003
Number Of Securities Total	12	15	15
Fair Value Total	2,744	3,247	3,074
Unrealized Losses Total	3,015	3,765	4,053
Mortgage Backed Securities Excluding Collateralized Mortgage Obligations [Member]
Number Of Securities Less than 12 Months	3	0	0
Fair Value Less than 12 Months	26,186	0	0
Unrealized Losses Less than 12 Months	150	0	0
Number Of Securities 12 Months or Longer	1	1	1
Fair Value 12 Months or Longer	454	577	581
Unrealized Losses 12 Months or Longer	1	16	17
Number Of Securities Total	4	1	1
Fair Value Total	26,640	577	581
Unrealized Losses Total	151	16	17
Collateralized Mortgage Obligations [Member]
Number Of Securities Less than 12 Months	2	16	5
Fair Value Less than 12 Months	14,733	88,673	39,299
Unrealized Losses Less than 12 Months	33	3,359	529
Number Of Securities 12 Months or Longer	25	14	14
Fair Value 12 Months or Longer	88,185	34,310	37,215
Unrealized Losses 12 Months or Longer	3,867	2,759	1,600
Number Of Securities Total	27	30	19
Fair Value Total	102,918	122,983	76,514
Unrealized Losses Total	3,900	6,118	2,129
Other Securities [Member]
Number Of Securities Less than 12 Months	0	2	2
Fair Value Less than 12 Months	0	1,977	1,930
Unrealized Losses Less than 12 Months	0	29	76
Number Of Securities 12 Months or Longer	2	1	1
Fair Value 12 Months or Longer	1,815	685	790
Unrealized Losses 12 Months or Longer	180	311	205
Number Of Securities Total	2	3	3
Fair Value Total	1,815	2,662	2,720
Unrealized Losses Total	$ 180	$ 340	$ 281