Loans And Allowance For Credit Losses (Narrative) (Details)		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) mo Billing_Cycles d Payments	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Loans And Allowance For Credit Losses [Line Items]
Unfunded Lending Commitments on Troubled Debt Restructuring		$ 3,600,000		$ 3,600,000		$ 3,600,000		$ 6,100,000
Loans and Leases Receivable, Gross		40,113,123,000		40,113,123,000		40,113,123,000		40,063,658,000
Financing Receivable, Recorded Investment, Current		39,794,516,000		39,794,516,000		39,794,516,000		39,796,072,000
Certain Loans Account for as Cash Basis, Net Carrying Amounts								5,300,000
Threshold for Internal risk grades assigned to commercial and commercial real estate loans		750,000		750,000		750,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses		800,000	$ 0	300,000	$ (2,500,000)
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		604,000	2,265,000	2,475,000	2,466,000	93,400,000	$ 97,300,000
Unearned income and fees, net of related costs		144,100,000		144,100,000		144,100,000		144,700,000
Owner occupied and commercial real estate loans, unamortized premiums		28,800,000		28,800,000		28,800,000		36,500,000
Land Development Loans		383,100,000		383,100,000		383,100,000		484,900,000
Loans at carrying value pledged as collateral for current and potential borrowings		22,300,000,000		22,300,000,000		22,300,000,000		22,500,000,000
Payments for Origination and Purchases of Loans Held-for-sale		442,400,000	297,800,000	1,111,000,000	894,900,000
Loans and Leases Receivable, Gain (Loss) on Sales, Net		5,000,000	4,200,000	13,900,000	11,300,000
Principle amount of loans held for sale sold		434,100,000	341,300,000	1,070,200,000	939,000,000
Servicing Retained for Loans Sold		1,200,000,000		1,200,000,000		1,200,000,000
Servicing Asset at Amortized Cost		0		$ 0		0		0
Number of days for consumer loans to be charged off | d				180
Number of days for closed-end loans to be charged off | d				120
Minimum number of days past due for nonaccrual status | d				90
Minimum number of monthly payments in arrears when reporting past due | Payments				2
Minimum number of billing cycles in arrears when reported as past due | Billing_Cycles				2
Minimum number of days unpaid when reported as past due | d				30
Threshold for nonaccrual loans for evaluation of impairment				$ 1,000,000
Minimum number of months for borrower to meet terms For TDR status | mo				6
Recorded investment in TDR loans modified with interest rates below market		190,700,000		$ 190,700,000		190,700,000		219,300,000
Total reversal amount to ALLL		600,000	800,000	3,100,000	4,400,000
Additional interest income due to increased cash flows from acquired loans		5,400,000	7,700,000	22,100,000	37,900,000
Provision for Loan and Lease Losses		18,262,000	(54,643,000)	17,334,000	(109,669,000)
Provision for Unfunded Lending Commitments		(1,428,000)	16,095,000	(313,000)	10,328,000
Other Real Estate, Foreclosed Assets, and Repossessed Assets		1,600,000		1,600,000		1,600,000
Other Real Estate, In Process of Forecloseing Assets		9,300,000		9,300,000		9,300,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		166,927,000		166,927,000		166,927,000		104,491,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		151,680,000		151,680,000		151,680,000		163,095,000
Financing Receivable, Recorded Investment, Past Due		318,607,000		318,607,000		318,607,000		267,586,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		34,857,000		34,857,000		34,857,000		29,228,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	193,883,000		193,883,000		193,883,000		154,778,000
Commercial [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		21,203,650,000		$ 21,203,650,000		21,203,650,000		21,444,364,000
Subsequent payment default period, number of days | d				90
Provision for Loan and Lease Losses		22,417,000	(19,960,000)	$ 53,292,000	(38,274,000)
Provision for Unfunded Lending Commitments		(2,808,000)	(1,651,000)	(4,651,000)	(6,107,000)
Consumer Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		8,606,750,000		$ 8,606,750,000		8,606,750,000		8,506,286,000
Subsequent payment default period, number of days | d				60
Provision for Loan and Lease Losses		2,466,000	(496,000)	$ 2,533,000	(14,045,000)
Provision for Unfunded Lending Commitments		(87,000)	3,356,000	(7,000)	3,249,000
Financing Receivable, Recorded Investment, Nonaccrual Status		272,000		272,000		272,000		254,000
Consumer Loan [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		8,606,750,000		8,606,750,000		8,606,750,000		8,506,286,000
Financing Receivable, Recorded Investment, Current		8,549,111,000		8,549,111,000		8,549,111,000		8,442,742,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		22,853,000		22,853,000		22,853,000		29,663,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		34,786,000		34,786,000		34,786,000		33,881,000
Financing Receivable, Recorded Investment, Past Due		57,639,000		57,639,000		57,639,000		63,544,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		1,664,000		1,664,000		1,664,000		1,425,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	21,892,000		21,892,000		21,892,000		23,150,000
Consumer Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		192,985,000		192,985,000		192,985,000		212,360,000
Financing Receivable, Recorded Investment, Current		192,042,000		192,042,000		192,042,000		211,560,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		877,000		877,000		877,000		644,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		66,000		66,000		66,000		156,000
Financing Receivable, Recorded Investment, Past Due		943,000		943,000		943,000		800,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0		0		0
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	46,000		46,000		46,000		84,000
Commercial and Industrial Sector [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		13,035,251,000		13,035,251,000		13,035,251,000		13,162,955,000
Financing Receivable, Recorded Investment, Current		12,909,622,000		12,909,622,000		12,909,622,000		13,092,731,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		79,246,000		79,246,000		79,246,000		28,295,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		46,383,000		46,383,000		46,383,000		41,929,000
Financing Receivable, Recorded Investment, Past Due		125,629,000		125,629,000		125,629,000		70,224,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		4,951,000		4,951,000		4,951,000		4,677,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	90,584,000		90,584,000		90,584,000		64,385,000
Finance Leases Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		426,781,000		426,781,000		426,781,000		408,974,000
Financing Receivable, Recorded Investment, Current		423,071,000		423,071,000		423,071,000		408,724,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		3,557,000		3,557,000		3,557,000		225,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		153,000		153,000		153,000		25,000
Financing Receivable, Recorded Investment, Past Due		3,710,000		3,710,000		3,710,000		250,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0		0		0
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	55,000		55,000		55,000		270,000
Owner Occupied [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		7,141,360,000		7,141,360,000		7,141,360,000		7,351,548,000
Financing Receivable, Recorded Investment, Current		7,077,386,000		7,077,386,000		7,077,386,000		7,275,842,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		33,198,000		33,198,000		33,198,000		29,182,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		30,776,000		30,776,000		30,776,000		46,524,000
Financing Receivable, Recorded Investment, Past Due		63,974,000		63,974,000		63,974,000		75,706,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		5,443,000		5,443,000		5,443,000		3,334,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	46,283,000		46,283,000		46,283,000		39,649,000
Municipal [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		600,258,000		600,258,000		600,258,000		520,887,000
Financing Receivable, Recorded Investment, Current		600,210,000		600,210,000		600,210,000		520,887,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		48,000		48,000		48,000		0
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		0		0		0		0
Financing Receivable, Recorded Investment, Past Due		48,000		48,000		48,000		0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0		0		0
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	967,000		967,000		967,000		1,056,000
Commercial Loan [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		21,203,650,000		21,203,650,000		21,203,650,000		21,444,364,000
Financing Receivable, Recorded Investment, Current		21,010,289,000		21,010,289,000		21,010,289,000		21,298,184,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		116,049,000		116,049,000		116,049,000		57,702,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		77,312,000		77,312,000		77,312,000		88,478,000
Financing Receivable, Recorded Investment, Past Due		193,361,000		193,361,000		193,361,000		146,180,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		10,394,000		10,394,000		10,394,000		8,011,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	137,889,000		137,889,000		137,889,000		105,360,000
Commercial Real Estate [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		2,213,465,000		2,213,465,000		2,213,465,000		1,986,408,000
Financing Receivable, Recorded Investment, Current		2,195,193,000		2,195,193,000		2,195,193,000		1,972,206,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		12,447,000		12,447,000		12,447,000		2,711,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		5,825,000		5,825,000		5,825,000		11,491,000
Financing Receivable, Recorded Investment, Past Due		18,272,000		18,272,000		18,272,000		14,202,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		2,296,000		2,296,000		2,296,000		92,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	10,914,000		10,914,000		10,914,000		12,481,000
Term [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		8,089,258,000		8,089,258,000		8,089,258,000		8,126,600,000
Financing Receivable, Recorded Investment, Current		8,039,923,000		8,039,923,000		8,039,923,000		8,082,940,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		15,578,000		15,578,000		15,578,000		14,415,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		33,757,000		33,757,000		33,757,000		29,245,000
Financing Receivable, Recorded Investment, Past Due		49,335,000		49,335,000		49,335,000		43,660,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		20,503,000		20,503,000		20,503,000		19,700,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	23,188,000		23,188,000		23,188,000		13,787,000
Commercial Real Estate [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		10,302,723,000		10,302,723,000		10,302,723,000		10,113,008,000
Financing Receivable, Recorded Investment, Current		10,235,116,000		10,235,116,000		10,235,116,000		10,055,146,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		28,025,000		28,025,000		28,025,000		17,126,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		39,582,000		39,582,000		39,582,000		40,736,000
Financing Receivable, Recorded Investment, Past Due		67,607,000		67,607,000		67,607,000		57,862,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		22,799,000		22,799,000		22,799,000		19,792,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	34,102,000		34,102,000		34,102,000		26,268,000
Home Equity Line of Credit [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		2,347,061,000		2,347,061,000		2,347,061,000		2,321,150,000
Financing Receivable, Recorded Investment, Current		2,336,740,000		2,336,740,000		2,336,740,000		2,309,967,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		4,694,000		4,694,000		4,694,000		4,503,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		5,627,000		5,627,000		5,627,000		6,680,000
Financing Receivable, Recorded Investment, Past Due		10,321,000		10,321,000		10,321,000		11,183,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0		0		1,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	2,592,000		2,592,000		2,592,000		1,779,000
One Through Four Family Residential [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		5,268,840,000		5,268,840,000		5,268,840,000		5,200,882,000
Financing Receivable, Recorded Investment, Current		5,231,005,000		5,231,005,000		5,231,005,000		5,163,610,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		10,137,000		10,137,000		10,137,000		12,416,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		27,698,000		27,698,000		27,698,000		24,856,000
Financing Receivable, Recorded Investment, Past Due		37,835,000		37,835,000		37,835,000		37,272,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		877,000		877,000		877,000		318,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	18,739,000		18,739,000		18,739,000		20,599,000
Construction And Other Consumer Real Estate [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		370,015,000		370,015,000		370,015,000		370,542,000
Financing Receivable, Recorded Investment, Current		364,283,000		364,283,000		364,283,000		359,723,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		5,524,000		5,524,000		5,524,000		9,675,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		208,000		208,000		208,000		1,144,000
Financing Receivable, Recorded Investment, Past Due		5,732,000		5,732,000		5,732,000		10,819,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0		0		160,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	401,000		401,000		401,000		608,000
Revolving Credit Facility [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		427,849,000		427,849,000		427,849,000		401,352,000
Financing Receivable, Recorded Investment, Current		425,041,000		425,041,000		425,041,000		397,882,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		1,621,000		1,621,000		1,621,000		2,425,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		1,187,000		1,187,000		1,187,000		1,045,000
Financing Receivable, Recorded Investment, Past Due		2,808,000		2,808,000		2,808,000		3,470,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		787,000		787,000		787,000		946,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	114,000		114,000		114,000		80,000
Accruing [Member]
Loans And Allowance For Credit Losses [Line Items]
Financing Receivable, Modifications, Recorded Investment		178,136,000		178,136,000		178,136,000		245,550,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		0	96,000	0	96,000
Nonaccruing [Member]
Loans And Allowance For Credit Losses [Line Items]
Financing Receivable, Modifications, Recorded Investment		286,523,000		286,523,000		286,523,000		343,329,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		604,000	$ 2,169,000	2,475,000	$ 2,370,000
Nonaccruing [Member] | Consumer Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 12,511,000		$ 12,511,000		$ 12,511,000		$ 21,074,000

[1] Represents nonaccrual loans that are not past due more than 30 days; however, full payment of principal and interest is still not expected.