Investment Securities (Gross Unrealized Losses and Fair Values by Investment and Length of Time Of Securities) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 69,197	$ 56,950
Unrealized Losses, Less than 12 Months	804	1,383
Fair Value, 12 Months or More	38,920	31,548
Unrealized Losses, 12 Months or More	17,167	17,627
Fair Value, Total	108,117	88,498
Unrealized Losses, Total	17,971	19,010
Obligations Of States And Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	39,233	31,791
Unrealized Losses, Less than 12 Months	476	295
Fair Value, 12 Months or More	7,176	0
Unrealized Losses, 12 Months or More	103	0
Fair Value, Total	46,409	31,791
Unrealized Losses, Total	579	295
Agency Residential Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	16,981	11,291
Unrealized Losses, Less than 12 Months	87	53
Fair Value, 12 Months or More	0	0
Unrealized Losses, 12 Months or More	0	0
Fair Value, Total	16,981	11,291
Unrealized Losses, Total	87	53
Non-Agency Residential Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	11,708	12,117
Unrealized Losses, Less than 12 Months	151	450
Fair Value, 12 Months or More	13,884	14,683
Unrealized Losses, 12 Months or More	1,052	1,530
Fair Value, Total	25,592	26,800
Unrealized Losses, Total	1,203	1,980
Other Structured Financial Products [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	0
Unrealized Losses, Less than 12 Months	0	0
Fair Value, 12 Months or More	9,977	9,551
Unrealized Losses, 12 Months or More	15,072	15,461
Fair Value, Total	9,977	9,551
Unrealized Losses, Total	15,072	15,461
Other Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	0
Unrealized Losses, Less than 12 Months	0	0
Fair Value, 12 Months or More	6,623	6,518
Unrealized Losses, 12 Months or More	372	464
Fair Value, Total	6,623	6,518
Unrealized Losses, Total	372	464
Other Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	1,275	1,751
Unrealized Losses, Less than 12 Months	90	585
Fair Value, 12 Months or More	1,260	796
Unrealized Losses, 12 Months or More	568	172
Fair Value, Total	2,535	2,547
Unrealized Losses, Total	$ 658	$ 757