Fair Values Of Assets And Liabilities (Narrative) (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 1,650,096,000	$ 1,650,096,000	$ 1,716,388,000	$ 2,214,281,000
Mortgage loans held-for-sale	559,634,000	559,634,000	388,038,000	347,005,000
Impaired loans—collateral based	90,540,000	$ 90,540,000	101,255,000	113,027,000
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for lack of market		10.00%
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,650,096,000	$ 1,650,096,000	1,716,388,000	2,214,281,000
MSRs	13,901,000	13,901,000	9,092,000	7,875,000
Remaining contractual principal balance outstanding, mortgage loans held-for-sale	537,000,000	537,000,000	372,000,000	328,100,000
Mortgage loans held-for-sale	559,634,000	559,634,000	388,038,000	347,005,000
Impaired loans—collateral based	64,600,000	64,600,000
Portion at Other than Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	25,900,000	25,900,000
Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	109,281,000	109,281,000	108,595,000	297,342,000
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	50,782,000	50,782,000	56,686,000	54,004,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
MSRs	13,901,000	13,901,000	9,092,000	7,875,000
Mortgage loans held-for-sale	559,634,000	559,634,000	388,038,000	347,005,000
Fair Value, Measurements, Recurring | Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	109,281,000	109,281,000	108,595,000	297,342,000
Fair Value, Measurements, Recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	50,782,000	50,782,000	56,686,000	54,004,000
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	64,614,000	64,614,000
Other real estate owned	45,449,000	45,449,000
Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
MSRs	13,901,000	13,901,000	9,092,000	7,875,000
Mortgage loans held-for-sale	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		3.00%
Fair Value Inputs, Prepayment Rate		2.00%
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		7.00%
Fair Value Inputs, Prepayment Rate		85.00%
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		5.52%
Fair Value Inputs, Prepayment Rate		14.73%
Level 3 | Fair Value, Measurements, Recurring | Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	67,208,000	$ 67,208,000	68,613,000	68,401,000
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	0	0	25,199,000	24,516,000
Gain on transfer	2,400,000
Level 3 | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	64,614,000	64,614,000
Other real estate owned	45,449,000	$ 45,449,000
Level 3 | Fair Value, Measurements, Nonrecurring | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for lack of market		10.00%
Level 3 | Fair Value, Measurements, Nonrecurring | Weighted Average | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for lack of market		10.00%
Non-performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held-for-sale	$ 0	$ 0	$ 0	$ 0