Loans And Allowance For Credit Losses (Narrative) (Details)		3 Months Ended		6 Months Ended		9 Months Ended
		Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) mo Billing_Cycles d Payments	Jun. 30, 2014 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Dec. 31, 2014 USD ($)
Loans And Allowance For Credit Losses [Line Items]
Unfunded Lending Commitments on Troubled Debt Restructuring		$ 3,700,000		$ 3,700,000				$ 6,100,000
Loans and Leases Receivable, Gross		40,023,984,000		40,023,984,000				40,063,658,000
Financing Receivable, Recorded Investment, Current		39,725,111,000		39,725,111,000				39,796,072,000
Certain Loans Account for as Cash Basis, Net Carrying Amounts		2,400,000		2,400,000				5,300,000
Threshold for Internal risk grades assigned to commercial and commercial real estate loans		750,000		750,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses		300,000	$ 200,000	(500,000)	$ (2,500,000)
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		2,186,000	837,000	3,145,000	1,054,000	$ 88,700,000	$ 141,300,000
Unearned income and fees, net of related costs		141,000,000		141,000,000				144,700,000
Owner occupied and commercial real estate loans, unamortized premiums		31,100,000		31,100,000				36,500,000
Land Development Loans		419,400,000		419,400,000				484,900,000
Loans at carrying value pledged as collateral for current and potential borrowings		22,400,000,000		22,400,000,000				22,500,000,000
Payments for Origination and Purchases of Loans Held-for-sale		359,000,000	301,600,000	668,700,000	597,100,000
Loans and Leases Receivable, Gain (Loss) on Sales, Net		4,300,000	3,600,000	8,900,000	7,100,000
Principle amount of loans held for sale sold		335,800,000	260,100,000	636,200,000	597,700,000
Servicing Asset at Amortized Cost		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		184,700,000		$ 184,700,000				219,300,000
Total reversal amount to ALLL		1,100,000	700,000	2,500,000	3,600,000
Additional interest income due to increased cash flows from acquired loans		9,300,000	11,700,000	16,700,000	30,200,000
Provision for Loan and Lease Losses		566,000	(54,416,000)	(928,000)	(55,026,000)
Provision for Unfunded Lending Commitments		2,326,000	(6,779,000)	1,115,000	(5,767,000)
Other Real Estate, Foreclosed Assets, and Repossessed Assets		1,400,000		1,400,000
Other Real Estate, In Process of Forecloseing Assets		10,100,000		10,100,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		144,995,000		144,995,000				104,491,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		153,878,000		153,878,000				163,095,000
Financing Receivable, Recorded Investment, Past Due		298,873,000		298,873,000				267,586,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		27,204,000		27,204,000				29,228,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	226,116,000		226,116,000				154,778,000
Commercial [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		21,378,666,000		$ 21,378,666,000				21,444,364,000
Subsequent payment default period, number of days | d				90
Provision for Loan and Lease Losses		5,941,000	(29,574,000)	$ 30,875,000	(18,314,000)
Provision for Unfunded Lending Commitments		(2,001,000)	(2,931,000)	1,843,000	4,456,000
Consumer Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		8,525,317,000		$ 8,525,317,000				8,506,286,000
Subsequent payment default period, number of days | d				60
Provision for Loan and Lease Losses		(392,000)	(4,570,000)	$ 67,000	(13,549,000)
Provision for Unfunded Lending Commitments		27,000	(432,000)	(80,000)	107,000
Financing Receivable, Recorded Investment, Nonaccrual Status		270,000		270,000				254,000
Consumer Loan [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		8,525,317,000		8,525,317,000				8,506,286,000
Financing Receivable, Recorded Investment, Current		8,457,535,000		8,457,535,000				8,442,742,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		39,751,000		39,751,000				29,663,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		28,031,000		28,031,000				33,881,000
Financing Receivable, Recorded Investment, Past Due		67,782,000		67,782,000				63,544,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		1,700,000		1,700,000				1,425,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	22,286,000		22,286,000				23,150,000
Consumer Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		202,434,000		202,434,000				212,360,000
Financing Receivable, Recorded Investment, Current		201,538,000		201,538,000				211,560,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		519,000		519,000				644,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		377,000		377,000				156,000
Financing Receivable, Recorded Investment, Past Due		896,000		896,000				800,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		141,000		141,000				0
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	4,000		4,000				84,000
Commercial and Industrial Sector [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		13,110,925,000		13,110,925,000				13,162,955,000
Financing Receivable, Recorded Investment, Current		13,007,655,000		13,007,655,000				13,092,731,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		64,040,000		64,040,000				28,295,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		39,230,000		39,230,000				41,929,000
Financing Receivable, Recorded Investment, Past Due		103,270,000		103,270,000				70,224,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		2,221,000		2,221,000				4,677,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	117,874,000		117,874,000				64,385,000
Finance Leases Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		401,548,000		401,548,000				408,974,000
Financing Receivable, Recorded Investment, Current		401,490,000		401,490,000				408,724,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		30,000		30,000				225,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		28,000		28,000				25,000
Financing Receivable, Recorded Investment, Past Due		58,000		58,000				250,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0				0
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	123,000		123,000				270,000
Owner Occupied [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		7,277,208,000		7,277,208,000				7,351,548,000
Financing Receivable, Recorded Investment, Current		7,207,298,000		7,207,298,000				7,275,842,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		24,480,000		24,480,000				29,182,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		45,430,000		45,430,000				46,524,000
Financing Receivable, Recorded Investment, Past Due		69,910,000		69,910,000				75,706,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		5,233,000		5,233,000				3,334,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	44,423,000		44,423,000				39,649,000
Municipal [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		588,985,000		588,985,000				520,887,000
Financing Receivable, Recorded Investment, Current		588,985,000		588,985,000				520,887,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		0		0				0
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		0		0				0
Financing Receivable, Recorded Investment, Past Due		0		0				0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0				0
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	992,000		992,000				1,056,000
Commercial Loan [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		21,378,666,000		21,378,666,000				21,444,364,000
Financing Receivable, Recorded Investment, Current		21,205,428,000		21,205,428,000				21,298,184,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		88,550,000		88,550,000				57,702,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		84,688,000		84,688,000				88,478,000
Financing Receivable, Recorded Investment, Past Due		173,238,000		173,238,000				146,180,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		7,454,000		7,454,000				8,011,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	163,412,000		163,412,000				105,360,000
Commercial Real Estate [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		2,061,716,000		2,061,716,000				1,986,408,000
Financing Receivable, Recorded Investment, Current		2,046,961,000		2,046,961,000				1,972,206,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		5,172,000		5,172,000				2,711,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		9,583,000		9,583,000				11,491,000
Financing Receivable, Recorded Investment, Past Due		14,755,000		14,755,000				14,202,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		220,000		220,000				92,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	10,821,000		10,821,000				12,481,000
Term [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		8,058,285,000		8,058,285,000				8,126,600,000
Financing Receivable, Recorded Investment, Current		8,015,187,000		8,015,187,000				8,082,940,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		11,522,000		11,522,000				14,415,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		31,576,000		31,576,000				29,245,000
Financing Receivable, Recorded Investment, Past Due		43,098,000		43,098,000				43,660,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		17,830,000		17,830,000				19,700,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	29,597,000		29,597,000				13,787,000
Commercial Real Estate [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		10,120,001,000		10,120,001,000				10,113,008,000
Financing Receivable, Recorded Investment, Current		10,062,148,000		10,062,148,000				10,055,146,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		16,694,000		16,694,000				17,126,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		41,159,000		41,159,000				40,736,000
Financing Receivable, Recorded Investment, Past Due		57,853,000		57,853,000				57,862,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		18,050,000		18,050,000				19,792,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	40,418,000		40,418,000				26,268,000
Home Equity Line of Credit [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		2,348,327,000		2,348,327,000				2,321,150,000
Financing Receivable, Recorded Investment, Current		2,338,099,000		2,338,099,000				2,309,967,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		4,318,000		4,318,000				4,503,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		5,910,000		5,910,000				6,680,000
Financing Receivable, Recorded Investment, Past Due		10,228,000		10,228,000				11,183,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		0		0				1,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	2,149,000		2,149,000				1,779,000
One Through Four Family Residential [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		5,193,463,000		5,193,463,000				5,200,882,000
Financing Receivable, Recorded Investment, Current		5,161,636,000		5,161,636,000				5,163,610,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		11,789,000		11,789,000				12,416,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		20,038,000		20,038,000				24,856,000
Financing Receivable, Recorded Investment, Past Due		31,827,000		31,827,000				37,272,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		744,000		744,000				318,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	19,351,000		19,351,000				20,599,000
Construction And Other Consumer Real Estate [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		371,622,000		371,622,000				370,542,000
Financing Receivable, Recorded Investment, Current		349,205,000		349,205,000				359,723,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		21,743,000		21,743,000				9,675,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		674,000		674,000				1,144,000
Financing Receivable, Recorded Investment, Past Due		22,417,000		22,417,000				10,819,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		135,000		135,000				160,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	590,000		590,000				608,000
Revolving Credit Facility [Member]
Loans And Allowance For Credit Losses [Line Items]
Loans and Leases Receivable, Gross		409,471,000		409,471,000				401,352,000
Financing Receivable, Recorded Investment, Current		407,057,000		407,057,000				397,882,000
Financing Receivable Recorded Investment Thirty To Eighty Nine Days Past Due		1,382,000		1,382,000				2,425,000
Financing Receivable Recorded Investments, Equal To and Greater Than 90 Days Past Due		1,032,000		1,032,000				1,045,000
Financing Receivable, Recorded Investment, Past Due		2,414,000		2,414,000				3,470,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		680,000		680,000				946,000
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	192,000		192,000				80,000
Accruing [Member]
Loans And Allowance For Credit Losses [Line Items]
Financing Receivable, Modifications, Recorded Investment		180,146,000		180,146,000				245,550,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		0	10,000	0	10,000
Nonaccruing [Member]
Loans And Allowance For Credit Losses [Line Items]
Financing Receivable, Modifications, Recorded Investment		298,504,000		298,504,000				343,329,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment		2,186,000	$ 827,000	3,145,000	$ 1,044,000
Nonaccruing [Member] | Consumer Portfolio Segment [Member]
Loans And Allowance For Credit Losses [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 11,798,000		$ 11,798,000				$ 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.