Schedule Of Valuation Techniques And Significant Unobservable Inputs Used To Measure Both Recurring And Non-Recurring (Detail) (USD $) In Thousands, unless otherwise specified						9 Months Ended						9 Months Ended				9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Municipal Bonds [Member]	Dec. 31, 2011 Municipal Bonds [Member]	Sep. 30, 2012 Municipal Bonds [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Municipal Bonds [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Municipal Bonds [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Municipal Bonds [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Equity Securities Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Equity Securities Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Equity Securities Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Equity Securities Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Mortgage Servicing Rights Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2012 Impaired Loans [Member] Fair Value, Measurements, Nonrecurring [Member]	Sep. 30, 2012 Impaired Loans [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Nonrecurring [Member]	Sep. 30, 2012 Other Real Estate Owned [Member] Fair Value, Measurements, Nonrecurring [Member]	Sep. 30, 2012 Other Real Estate Owned [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	$ 1,256,768	$ 1,291,797	$ 1,267,682					$ 99,384	$ 60,098	$ 99,384	$ 62,307	$ 35,755	$ 25,405	$ 40,717	$ 43,032	$ 22,255	$ 30,891
Fair Value Of Mortgage Servicing Rights				6,276	6,740		6,740											6,276
Fair Value																			$ 147,979		$ 67,377
Valuation Methodology												Bond pricing				Discounted cash flows		Discounted cash flows		Appraisal value		Appraisal value
Significant Unobservable Input						Constant prepayment rate (CPR)						Equivalent rating				Discount rate		Discount rate		N/A		Property specific impairment adjustment
Level 3 Fair Value Measurements Range of Inputs						21%-26%						BBB-AAA				2.03%-2.41%		10%-13.5%				0%-61%
Weighted Average of Inputs						22.31%										2.25%		10.22%				5.43%
Impact to valuation from an increased or higher input value						Decrease						Increase				Decrease		Decrease				Decrease