Troubled Debts Restructured (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012 Investment	Jun. 30, 2012 Investment
Commercial | Real estate
Financing Receivable, Modifications [Line Items]
No. of Loans	2	3
Pre-Modification Outstanding Recorded Balance	$ 518	$ 921
Post-Modification Outstanding Recorded Balance	678	1,081
Commercial | Other
Financing Receivable, Modifications [Line Items]
No. of Loans	2	3
Pre-Modification Outstanding Recorded Balance	119	216
Post-Modification Outstanding Recorded Balance	181	277
Residential Mortgage
Financing Receivable, Modifications [Line Items]
No. of Loans	10	19
Pre-Modification Outstanding Recorded Balance	1,008	1,736
Post-Modification Outstanding Recorded Balance	1,110	1,861
Consumer loans | Real estate
Financing Receivable, Modifications [Line Items]
No. of Loans	3	10
Pre-Modification Outstanding Recorded Balance	66	391
Post-Modification Outstanding Recorded Balance	67	393
Consumer loans | Auto
Financing Receivable, Modifications [Line Items]
No. of Loans	1	1
Pre-Modification Outstanding Recorded Balance	8	7
Post-Modification Outstanding Recorded Balance	8	7
Consumer loans | Boat/RV
Financing Receivable, Modifications [Line Items]
No. of Loans	2	3
Pre-Modification Outstanding Recorded Balance	48	58
Post-Modification Outstanding Recorded Balance	48	58
Consumer loans | Other
Financing Receivable, Modifications [Line Items]
No. of Loans	2	2
Pre-Modification Outstanding Recorded Balance	15	16
Post-Modification Outstanding Recorded Balance	$ 14	$ 15