Fair Value Measurement (Fair Value Disclosure Table) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Financial assets:
Cash and Cash Equivalents, at Carrying Value	$ 347,103	$ 258,014	$ 489,985	$ 377,319
Cash and due from banks, Fair Value	347,103	258,014	489,985
Available-for-sale Securities, Carrying Amount	3,243,835	2,920,971	3,491,647
Available-for-sale Securities, Fair Value Disclosure	3,243,835	2,920,971	3,491,647
Held-to-maturity Securities, Carrying Amount	665,589	622,121	100,840
Held-to-maturity Securities, Fair Value Disclosure	673,501	630,799	103,865
Other Investments, Carrying Amount	140,984	140,717	140,713
Other Investments, Fair Value	140,984	140,717	140,713
Loans Receivable Held-for-sale, Carrying Amount	14,459	23,683	42,447
Loans Held-for-sale, Fair Value Disclosure	14,459	23,683	42,447
Loans and Leases Receivable, Carrying Amount	8,681,127	8,632,717	7,759,360
Net noncovered loans, Fair Value	8,649,899	8,604,872	7,496,821
Net covered loans and loss share receivable, Carrying Amount	848,887	975,870	1,337,080
Net covered loans and loss share receivable, Fair Value	848,887	975,870	1,337,080
Accrued interest receivable, Carrying Amount	43,701	40,389	45,270
Accrued interest receivable, Fair Value	43,701	40,389	45,270
Derivative Assets, Carrying Amount	58,563	63,169	60,115
Derivative Asset, Fair Value, Gross Asset	58,563	63,169	60,115
Financial liabilities:
Deposits, Carrying Amount	11,925,767	11,759,425	11,648,165
Deposits, Fair Value	11,931,015	11,765,873	11,659,976
Total Federal funds purchased and securities sold under agreements to repurchase, Carrying Amount	826,855	1,104,525	928,760
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	826,855	1,104,525	928,760
Wholesale Borrowings, Carrying Amount	136,003	136,883	176,611
Other Borrowings, Fair Value	141,613	143,029	184,640
Accrued interest payable, Carrying Amount	3,853	2,515	3,350
Accrued interest payable, Fair Value	3,853	2,515	3,350
Derivative liabilities, Carrying Amount	71,933	77,906	80,174
Derivative Liability, Fair Value, Gross Liability	71,933	77,906	80,174
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and due from banks, Fair Value	0	0	0
Available-for-sale Securities, Fair Value Disclosure	3,212	3,241	3,308
Held-to-maturity Securities, Fair Value Disclosure	0	0	0
Other Investments, Fair Value	0	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0	0
Net noncovered loans, Fair Value	0	0	0
Net covered loans and loss share receivable, Fair Value	0	0	0
Accrued interest receivable, Fair Value	0	0	0
Derivative Asset, Fair Value, Gross Asset	0	0	0
Financial liabilities:
Deposits, Fair Value	0	0	0
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	0	0	0
Other Borrowings, Fair Value	0	0	0
Accrued interest payable, Fair Value	0	0	0
Derivative Liability, Fair Value, Gross Liability	0	0	0
Fair Value, Inputs, Level 2 [Member]
Financial assets:
Cash and due from banks, Fair Value	347,103	258,014	489,985
Available-for-sale Securities, Fair Value Disclosure	3,189,389	2,868,069	3,399,852
Held-to-maturity Securities, Fair Value Disclosure	673,501	630,799	103,865
Other Investments, Fair Value	140,984	140,717	140,713
Loans Held-for-sale, Fair Value Disclosure	14,459	23,683	42,447
Net noncovered loans, Fair Value	0	0	0
Net covered loans and loss share receivable, Fair Value	0	0	0
Accrued interest receivable, Fair Value		40,389	45,270
Derivative Asset, Fair Value, Gross Asset	58,563	63,169	60,115
Financial liabilities:
Deposits, Fair Value	11,931,015	11,765,873	11,659,976
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	826,855	1,104,525	928,760
Other Borrowings, Fair Value	141,613	143,029	184,640
Accrued interest payable, Fair Value		2,515	3,350
Derivative Liability, Fair Value, Gross Liability	71,933	77,906	80,174
Fair Value, Inputs, Level 3 [Member]
Financial assets:
Cash and due from banks, Fair Value	0	0	0
Available-for-sale Securities, Fair Value Disclosure	51,234	49,661	88,487
Held-to-maturity Securities, Fair Value Disclosure	0	0	0
Other Investments, Fair Value	0	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0	0
Net noncovered loans, Fair Value	8,649,899	8,604,872	7,496,821
Net covered loans and loss share receivable, Fair Value	848,887	975,870	1,337,080
Accrued interest receivable, Fair Value	0	0	0
Derivative Asset, Fair Value, Gross Asset	0	0	0
Financial liabilities:
Deposits, Fair Value	0	0	0
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	0	0	0
Other Borrowings, Fair Value	0	0	0
Accrued interest payable, Fair Value	0	0	0
Derivative Liability, Fair Value, Gross Liability	$ 0	$ 0	$ 0