Fair Value Measurement (Fair Value Disclosure Table) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Financial assets:
Cash and Cash Equivalents, at Carrying Value	$ 1,247,267	$ 258,014	$ 238,417	$ 377,319
Cash and due from banks, Fair Value	1,247,267	258,014	238,417
Available-for-sale Securities, Carrying Amount	3,256,259	2,920,971	2,911,993
Held-to-maturity Securities, Carrying Amount	2,749,934	622,121	620,631
Held-to-maturity Securities, Fair Value Disclosure	2,658,433	630,799	631,237
Other Investments, Carrying Amount	270,369	140,717	140,730
Other Investments, Fair Value	270,369	140,717	140,730
Loans Receivable Held-for-sale, Carrying Amount	17,813	23,683	17,540
Loans Held-for-sale, Fair Value Disclosure	17,813	23,683	17,540
Loans and Leases Receivable, Carrying Amount	9,690,848	8,632,717	8,217,478
Net noncovered loans, Fair Value	9,623,848	8,604,872	7,898,195
Net covered loans and loss share receivable, Carrying Amount	608,732	975,870	1,131,285
Net covered loans and loss share receivable, Fair Value	608,732	975,870	1,131,285
Accrued interest receivable, Carrying Amount	49,820	40,389	43,901
Accrued interest receivable, Fair Value	49,820	40,389	43,901
Derivative Assets, Carrying Amount	53,839	63,231	70,270
Derivative Asset, Fair Value, Gross Asset	53,839	63,231	70,270
Financial liabilities:
Deposits, Carrying Amount	19,489,533	11,759,425	11,532,426
Deposits, Fair Value	19,508,531	11,765,873	11,540,681
Total Federal funds purchased and securities sold under agreements to repurchase, Carrying Amount	1,049,801	1,104,525	963,455
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	1,049,801	1,104,525	963,455
Wholesale Borrowings, Carrying Amount	200,858	136,883	178,083
Other Borrowings, Fair Value	204,461	143,029	187,230
Long-term Debt	324,425	0	0
Long-term Debt, Fair Value	321,255
Accrued interest payable, Carrying Amount	5,884	2,515	2,798
Accrued interest payable, Fair Value	5,884	2,515	2,798
Derivative liabilities, Carrying Amount	65,506	77,968	87,161
Derivative Liability, Fair Value, Gross Liability	65,506	77,968	87,161
Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, Fair Value	1,247,267	258,014	238,417
Available-for-sale Securities, Carrying Amount	3,096	3,241	3,245
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
Long-term Debt, Fair Value	0
Accrued interest payable, Fair Value	0	0	0
Derivative Liability, Fair Value, Gross Liability	0	0	0
Fair Value, Inputs, Level 2
Financial assets:
Cash and due from banks, Fair Value	0	0	0
Available-for-sale Securities, Carrying Amount	2,930,401	2,868,069	2,861,244
Held-to-maturity Securities, Fair Value Disclosure	2,658,433	630,799	631,237
Other Investments, Fair Value	270,369	140,717	140,730
Loans Held-for-sale, Fair Value Disclosure	17,813	23,683	17,540
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	49,820	40,389	43,901
Derivative Asset, Fair Value, Gross Asset	53,839	63,231	70,270
Financial liabilities:
Deposits, Fair Value	19,508,531	11,765,873	11,540,681
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	1,049,801	1,104,525	963,455
Other Borrowings, Fair Value	204,461	143,029	187,230
Long-term Debt, Fair Value	321,255
Accrued interest payable, Fair Value	5,884	2,515	2,798
Derivative Liability, Fair Value, Gross Liability	65,506	77,968	87,161
Fair Value, Inputs, Level 3
Financial assets:
Cash and due from banks, Fair Value	0	0	0
Available-for-sale Securities, Carrying Amount	322,762	49,661	47,504
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	9,623,848	8,604,872	7,898,195
Net covered loans and loss share receivable, Fair Value	608,732	975,870	1,131,285
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
Long-term Debt, Fair Value	0
Accrued interest payable, Fair Value	0	0	0
Derivative Liability, Fair Value, Gross Liability	0	0	0
Acquired Loans
Financial assets:
Net noncovered loans, Fair Value	3,825,751
Acquired Loans | Fair Value, Inputs, Level 1
Financial assets:
Net noncovered loans, Fair Value	0
Acquired Loans | Fair Value, Inputs, Level 2
Financial assets:
Net noncovered loans, Fair Value	0
Acquired Loans | Fair Value, Inputs, Level 3
Financial assets:
Net noncovered loans, Fair Value	$ 3,825,751