Fair Values Of Assets And Liabilities (Narrative) (Detail) (USD $)	3 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 1,781,883,000	$ 1,796,076,000	$ 1,256,768,000
Mortgages held for sale, past due 90 days and accruing	0	0	0
Total impaired loans	176,298,000	204,545,000	233,014,000
Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	150,647,000	110,471,000	99,384,000
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	49,271,000	49,699,000	40,717,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights	8,608,000	6,750,000	6,276,000
Mortgage loans held-for-sale	329,186,000	385,033,000	548,300,000
Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	150,647,000	110,471,000	99,384,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	49,271,000	49,699,000	40,717,000
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Loans Fair Value Disclosure	97,093,000
Other real estate owned	142,287,000
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights	8,608,000	6,750,000	6,276,000
Mortgage loans held-for-sale	0	0	0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	32,688,000	30,770,000	35,755,000
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	20,442,000	22,169,000	22,255,000
Level Three Fair Value Measurements Weighted Average Percentage	2.28%
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	1.83%
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	2.71%
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	2.28%
Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Loans Fair Value Disclosure	97,093,000
Other real estate owned	142,287,000
Level 3 [Member] | Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level Three Fair Value Measurements Weighted Average Percentage	1.87%
Level 3 [Member] | Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	0.00%
Level 3 [Member] | Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	48.00%
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Remaining contractual principal balance outstanding, mortgage loans held-for-sale	310,300,000	379,500,000	537,200,000
Valued Using Discounted Cash Flow Model [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impaired loans	$ 79,200,000
Mortgage Servicing Rights [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	10.00%
Fair Value Inputs, Prepayment Rate	11.00%
Mortgage Servicing Rights [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	13.50%
Fair Value Inputs, Prepayment Rate	17.00%
Mortgage Servicing Rights [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	10.17%
Fair Value Inputs, Prepayment Rate	13.55%