Fair Values Of Assets And Liabilities (Narrative) (Detail) - USD ($)		3 Months Ended	6 Months Ended
		Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		$ 2,162,061,000	$ 2,162,061,000	$ 1,792,078,000	$ 1,824,240,000
Mortgage loans held-for-sale, at fair value		497,283,000	497,283,000	351,290,000	363,627,000
Impaired loans—collateral based	[1]	103,357,000	103,357,000	127,412,000	137,245,000
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		2,162,061,000	2,162,061,000	1,792,078,000	1,824,240,000
Mortgage servicing rights		8,034,000	8,034,000	8,435,000	8,227,000
Remaining contractual principal balance outstanding, mortgage loans held-for-sale		475,900,000	475,900,000	327,100,000	340,500,000
Mortgage loans held-for-sale, at fair value		497,283,000	497,283,000	351,290,000	363,627,000
Impaired loans—collateral based		61,700,000	61,700,000
Portion at Other than Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based		41,700,000	41,700,000
Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		269,790,000	269,790,000	238,529,000	176,107,000
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		54,208,000	54,208,000	51,139,000	54,852,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights		8,034,000	8,034,000	8,435,000	8,227,000
Mortgage loans held-for-sale, at fair value		497,283,000	497,283,000	351,290,000	363,627,000
Fair Value, Measurements, Recurring | Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		269,790,000	269,790,000	238,529,000	176,107,000
Fair Value, Measurements, Recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		54,208,000	54,208,000	51,139,000	54,852,000
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based		61,713,000	61,713,000
Other real estate owned	[2]	77,499,000	77,499,000
Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights		8,034,000	8,034,000	8,435,000	8,227,000
Mortgage loans held-for-sale, at fair value		$ 0	0	0	0
Level 3 | Fair Value, Measurements, Recurring | Minimum | Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		9.00%
Fair Value Inputs, Prepayment Rate		10.00%
Level 3 | Fair Value, Measurements, Recurring | Maximum | Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		13.00%
Fair Value Inputs, Prepayment Rate		25.00%
Level 3 | Fair Value, Measurements, Recurring | Weighted Average | Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		9.15%
Fair Value Inputs, Prepayment Rate		11.83%
Level 3 | Fair Value, Measurements, Recurring | Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		$ 58,572,000	58,572,000	58,953,000	38,053,000
Level 3 | Fair Value, Measurements, Recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value		$ 24,996,000	24,996,000	23,711,000	$ 24,152,000
Level 3 | Fair Value, Measurements, Recurring | Equity securities | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		1.77%
Level 3 | Fair Value, Measurements, Recurring | Equity securities | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		2.02%
Level 3 | Fair Value, Measurements, Recurring | Equity securities | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		1.86%
Level 3 | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based		$ 61,713,000	61,713,000
Other real estate owned		$ 77,499,000	$ 77,499,000
Level 3 | Fair Value, Measurements, Nonrecurring [Member] | Minimum | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Property Specific Valuation Adjustment		(85.00%)
Level 3 | Fair Value, Measurements, Nonrecurring [Member] | Maximum | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Property Specific Valuation Adjustment		87.00%
Level 3 | Fair Value, Measurements, Nonrecurring [Member] | Weighted Average | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Property Specific Valuation Adjustment			(3.58%)
Non-performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held-for-sale, at fair value		$ 0	$ 0	$ 0		$ 0

[1] Impaired loans are considered by the Company to be non-accrual loans, TDRs or loans with principal and/or interest at risk, even if the loan is current with all payments of principal and interest.

[2] Fair value losses recognized, net on other real estate owned include valuation adjustments and charge-offs during the respective period.