Fair Value Measurement (Fair Value Disclosure by Balance Sheet Grouping ) (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Mortgage Servicing Rights	$ 22,150,000	$ 22,604,000	$ 22,150,000	$ 22,604,000	$ 22,760,000	$ 22,469,000	$ 21,378,000	$ 21,316,000
Financial assets:
Cash and Cash Equivalents, at Carrying Value	642,570,000	909,490,000	642,570,000	909,490,000	917,822,000			258,014,000
Cash and due from banks, Fair Value	642,570,000	909,490,000	642,570,000	909,490,000	917,822,000
Available-for-sale Securities, Carrying Amount	3,478,420,000	3,299,392,000	3,478,420,000	3,299,392,000	3,273,174,000
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	3,052,118,000	2,551,860,000	3,052,118,000	2,551,860,000	2,935,688,000
Held-to-maturity Securities, Carrying Amount	3,052,118,000	2,551,860,000	3,052,118,000	2,551,860,000	2,935,688,000
Held-to-maturity Securities, Fair Value Disclosure	3,001,866,000	2,487,071,000	3,001,866,000	2,487,071,000	2,824,240,000
Other Investments, Carrying Amount	148,433,000	267,565,000	148,433,000	267,565,000	180,803,000
Other Investments, Fair Value	148,433,000	267,565,000	148,433,000	267,565,000	180,803,000
Loans Receivable Held-for-sale, Carrying Amount	21,632,000	22,855,000	21,632,000	22,855,000	11,622,000
Loans Held-for-sale, Fair Value Disclosure	21,632,000	22,855,000	21,632,000	22,855,000	11,622,000
Loans and Leases Receivable, Net Amount	14,827,591,000	13,995,709,000	14,827,591,000	13,995,709,000	14,159,720,000
Loans and Leases Receivable, Carrying Amount		9,033,980,000		9,033,980,000	10,116,903,000
Net noncovered loans, Fair Value	11,458,318,000	8,984,845,000	11,458,318,000	8,984,845,000	10,017,722,000
Net covered loans and loss share receivable, Carrying Amount		711,367,000		711,367,000	547,943,000
Net covered loans and loss share receivable, Fair Value	433,538,000	711,367,000	433,538,000	711,367,000	547,943,000
Accrued interest receivable, Carrying Amount	63,172,000	48,635,000	63,172,000	48,635,000	52,929,000
Accrued interest receivable, Fair Value	63,172,000	48,635,000	63,172,000	48,635,000	52,929,000
Derivative Assets, Carrying Amount	50,550,000	53,158,000	50,550,000	53,158,000	47,902,000
Derivative Asset, Fair Value, Gross Asset	50,550,000	53,158,000	50,550,000	53,158,000	47,902,000
Financial liabilities:
Deposits, Carrying Amount	19,298,396,000	19,119,722,000	19,298,396,000	19,119,722,000	19,533,601,000
Deposits, Fair Value	19,300,842,000	19,125,843,000	19,300,842,000	19,125,843,000	19,532,368,000
Total Federal funds purchased and securities sold under agreements to repurchase, Carrying Amount	1,218,855,000	844,871,000	1,218,855,000	844,871,000	851,535,000
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	1,218,855,000	844,871,000	1,218,855,000	844,871,000	851,535,000
Wholesale Borrowings, Carrying Amount	649,021,000	201,337,000	649,021,000	201,337,000	200,600,000
Other Borrowings, Fair Value	652,615,000	205,210,000	652,615,000	205,210,000	204,124,000
Long-term Debt	324,433,000	324,422,000	324,433,000	324,422,000	324,428,000
Long-term Debt, Fair Value	335,757,000	322,322,000	335,757,000	322,322,000	319,711,000
Accrued interest payable, Carrying Amount	8,311,000	9,066,000	8,311,000	9,066,000	9,339,000
Accrued interest payable, Fair Value	8,311,000	9,066,000	8,311,000	9,066,000	9,339,000
Derivative liabilities, Carrying Amount	57,544,000	62,217,000	57,544,000	62,217,000	58,201,000
Derivative Liability, Fair Value, Gross Liability	57,544,000	62,217,000	57,544,000	62,217,000	58,201,000
Mortgage Servicing rights Valuation Allowance	(562,000)	(482,000)	(562,000)	(482,000)	(282,000)	425,000	1,234,000	(2,564,000)
Mortgage Servicing Rights Net Carrying balance	21,588,000	22,122,000	21,588,000	22,122,000	22,500,000
Mortgage Servicing Rights (MSR) Impairment (Recovery)	(137,000)	752,000	(280,000)	(2,082,000)	2,300,000
Impaired Collateral Dependant Loans, Recorded Investment	62,200,000	58,100,000	62,200,000	58,100,000	52,600,000
Determination Of Specific Allowance For Loan Losses	(6,200,000)	(5,500,000)	(6,200,000)	(5,500,000)	(4,800,000)
Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, Fair Value		909,490,000		909,490,000	917,822,000
Available-for-sale Securities, Carrying Amount	2,935,000	3,213,000	2,935,000	3,213,000	3,036,000
Held-to-maturity Securities, Fair Value Disclosure	0	0	0	0	0
Other Investments, Fair Value	0	0	0	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0	0	0	0
Net noncovered loans, Fair Value	0	0	0	0	0
Net covered loans and loss share receivable, Fair Value	0	0	0	0	0
Accrued interest receivable, Fair Value	0	0	0	0	0
Derivative Asset, Fair Value, Gross Asset	0	0	0	0	0
Financial liabilities:
Deposits, Fair Value	0	0	0	0	0
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	0	0	0	0	0
Other Borrowings, Fair Value	0	0	0	0	0
Long-term Debt, Fair Value	0	0	0	0	0
Accrued interest payable, Fair Value	0	0	0	0	0
Derivative Liability, Fair Value, Gross Liability	0	0	0	0	0
Fair Value, Inputs, Level 2
Financial assets:
Cash and due from banks, Fair Value	0	0	0	0	0
Available-for-sale Securities, Carrying Amount	3,124,752,000	3,083,667,000	3,124,752,000	3,083,667,000	2,922,527,000
Held-to-maturity Securities, Fair Value Disclosure	3,001,866,000	2,487,071,000	3,001,866,000	2,487,071,000	2,824,240,000
Other Investments, Fair Value		267,565,000		267,565,000	180,803,000
Loans Receivable Held-for-sale, Carrying Amount	21,632,000		21,632,000
Loans Held-for-sale, Fair Value Disclosure		22,855,000		22,855,000	11,622,000
Net noncovered loans, Fair Value	0	0	0	0	0
Net covered loans and loss share receivable, Fair Value	0	0	0	0	0
Accrued interest receivable, Fair Value	63,172,000	48,635,000	63,172,000	48,635,000	52,929,000
Derivative Asset, Fair Value, Gross Asset	50,550,000	53,158,000	50,550,000	53,158,000	47,902,000
Financial liabilities:
Deposits, Fair Value	19,300,842,000	19,125,843,000	19,300,842,000	19,125,843,000	19,532,368,000
Federal funds purchased and securities sold under agreements to repurchase, Fair Value		844,871,000		844,871,000	851,535,000
Other Borrowings, Fair Value	652,615,000	205,210,000	652,615,000	205,210,000	204,124,000
Long-term Debt, Fair Value	335,757,000	322,322,000	335,757,000	322,322,000	319,711,000
Accrued interest payable, Fair Value	8,311,000	9,066,000	8,311,000	9,066,000	9,339,000
Derivative Liability, Fair Value, Gross Liability	57,544,000	62,217,000	57,544,000	62,217,000	58,201,000
Level 3
Financial assets:
Cash and due from banks, Fair Value	0	0	0	0	0
Available-for-sale Securities, Carrying Amount	350,733,000	212,512,000	350,733,000	212,512,000	347,611,000
Held-to-maturity Securities, Fair Value Disclosure	0	0	0	0	0
Other Investments, Fair Value	0	0	0	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0	0	0	0
Net noncovered loans, Fair Value	11,458,318,000	8,984,845,000	11,458,318,000	8,984,845,000	10,017,722,000
Net covered loans and loss share receivable, Fair Value	433,538,000	711,367,000	433,538,000	711,367,000	547,943,000
Accrued interest receivable, Fair Value	0	0	0	0	0
Derivative Asset, Fair Value, Gross Asset	0	0	0	0	0
Financial liabilities:
Deposits, Fair Value	0	0	0	0	0
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	0	0	0	0	0
Other Borrowings, Fair Value	0	0	0	0	0
Long-term Debt, Fair Value	0	0	0	0	0
Accrued interest payable, Fair Value	0	0	0	0	0
Derivative Liability, Fair Value, Gross Liability	0	0	0	0	0
Originated Loans
Financial assets:
Loans and Leases Receivable, Net Amount	11,375,243,000	9,033,980,000	11,375,243,000	9,033,980,000	10,116,903,000
Acquired Loans
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans Receivable, Fair Value Disclosure					3,627,275,000
Financial assets:
Loans and Leases Receivable, Net Amount	3,018,810,000		3,018,810,000		3,494,874,000
Net noncovered loans, Fair Value	3,166,228,000	4,250,362,000	3,166,228,000	4,250,362,000
Acquired Loans | Fair Value, Inputs, Level 1
Financial assets:
Net noncovered loans, Fair Value	0		0
Acquired Loans | Fair Value, Inputs, Level 2
Financial assets:
Net noncovered loans, Fair Value	0		0
Acquired Loans | Level 3
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loans Receivable, Fair Value Disclosure					3,627,275,000
Financial assets:
Net noncovered loans, Fair Value	$ 3,166,228,000	$ 4,250,362,000	$ 3,166,228,000	$ 4,250,362,000