Fair Value Of Assets and Liabilities (Schedule Of Valuation Techniques And Significant Unobservable Inputs Used To Measure Both Recurring And Non-Recurring) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	$ 1,870,831	$ 1,796,076	$ 1,869,344
Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Mortgage servicing rights	7,344	6,750	7,201
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Impaired loans - collateral based	121,200
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Mortgage servicing rights		6,750	7,201
Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Impaired loans - collateral based	121,197
Other real estate owned	56,177
Other Real Estate Owned [Member] | Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Other real estate owned	56,177
Valuation Methodology	Appraisal value
Significant Unobservable Input	Property specific impairment adjustment
Range of Inputs	0%-100%
Weighted Average of Inputs	4.44%
Impact to valuation from an increased or higher input value	Decrease
Impaired Loans [Member] | Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Impaired loans - collateral based	121,197
Valuation Methodology	Appraisal value
Municipal Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	110,259	110,471	69,915
Municipal Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	110,259	110,471	69,915
Municipal Bonds [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	32,324	30,770	25,535
Valuation Methodology	Bond pricing
Significant Unobservable Input	Equivalent rating
Range of Inputs	BBB-AAA
Impact to valuation from an increased or higher input value	Increase
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	52,057	49,699	38,496
Equity Securities [Member] | Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	1.39%
Equity Securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Available-for-sale securities	24,470	22,169	21,224
Valuation Methodology	Discounted cash flows
Significant Unobservable Input	Discount rate
Range of Inputs	1.20%-1.52%
Weighted Average of Inputs	1.39%
Impact to valuation from an increased or higher input value	Decrease
Mortgage Servicing Rights [Member] | Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	10.19%
Fair Value Inputs, Prepayment Rate	18.32%
Mortgage Servicing Rights [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Mortgage servicing rights	$ 7,344
Valuation Methodology	Discounted cash flows
Mortgage Servicing Rights Discount Rate Input [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Significant Unobservable Input	Discount rate
Range of Inputs	10%-13.5%
Weighted Average of Inputs	10.19%
Impact to valuation from an increased or higher input value	Decrease
Mortgage Servicing Rights Prepayment Rate Input [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Significant Unobservable Input	Constant prepayment rate (CPR)
Range of Inputs	16%-22%
Weighted Average of Inputs	18.32%
Impact to valuation from an increased or higher input value	Decrease
Maximum [Member] | Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	100.00%
Maximum [Member] | Other Real Estate Owned [Member] | Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Other Adjustments	100.00%
Maximum [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	1.52%
Maximum [Member] | Equity Securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	1.52%
Maximum [Member] | Mortgage Servicing Rights [Member] | Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	13.50%
Fair Value Inputs, Prepayment Rate	22.00%
Maximum [Member] | Mortgage Servicing Rights Discount Rate Input [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	13.50%
Maximum [Member] | Mortgage Servicing Rights Prepayment Rate Input [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Prepayment Rate	22.00%
Minimum [Member] | Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	0.00%
Minimum [Member] | Other Real Estate Owned [Member] | Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Other Adjustments	0.00%
Minimum [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	1.20%
Minimum [Member] | Equity Securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	1.20%
Minimum [Member] | Mortgage Servicing Rights [Member] | Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	10.00%
Fair Value Inputs, Prepayment Rate	16.00%
Minimum [Member] | Mortgage Servicing Rights Discount Rate Input [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	10.00%
Minimum [Member] | Mortgage Servicing Rights Prepayment Rate Input [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs, Prepayment Rate	16.00%