Fair Value Measurement (Fair Value Disclosure Table) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Financial assets:
Cash and Cash Equivalents, at Carrying Value	$ 909,490	$ 258,014	$ 337,935	$ 377,319
Cash and due from banks, Fair Value	909,490	258,014	337,935
Available-for-sale Securities, Carrying Amount	3,299,392	2,920,971	3,216,365
Available-for-sale Securities, Fair Value Disclosure	3,299,392	2,920,971	3,216,365
Held-to-maturity Securities, Carrying Amount	2,551,860	622,121	352,221
Held-to-maturity Securities, Fair Value Disclosure	2,487,071	630,799	355,120
Other Investments, Carrying Amount	267,565	140,717	140,742
Other Investments, Fair Value	267,565	140,717	140,742
Loans Receivable Held-for-sale, Carrying Amount	22,855	23,683	19,018
Loans Held-for-sale, Fair Value Disclosure	22,855	23,683	19,018
Loans and Leases Receivable, Carrying Amount	9,033,980	8,632,717	7,996,079
Net noncovered loans, Fair Value	8,984,845	8,604,872	7,677,176
Net covered loans and loss share receivable, Carrying Amount	711,367	975,870	1,229,282
Net covered loans and loss share receivable, Fair Value	711,367	975,870	1,229,282
Accrued interest receivable, Carrying Amount	48,635	40,389	43,727
Accrued interest receivable, Fair Value	48,635	40,389	43,727
Derivative Assets, Carrying Amount	53,158	63,231	66,619
Derivative Asset, Fair Value, Gross Asset	53,158	63,231	66,619
Financial liabilities:
Deposits, Carrying Amount	19,119,722	11,759,425	11,615,841
Deposits, Fair Value	19,125,843	11,765,873	11,625,406
Total Federal funds purchased and securities sold under agreements to repurchase, Carrying Amount	844,871	1,104,525	896,910
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	844,871	1,104,525	896,910
Wholesale Borrowings, Carrying Amount	201,337	136,883	178,135
Other Borrowings, Fair Value	205,210	143,029	186,458
Long-term Debt	324,422	0	0
Long-term Debt, Fair Value	322,322
Accrued interest payable, Carrying Amount	9,066	2,515	3,266
Accrued interest payable, Fair Value	9,066	2,515	3,266
Derivative liabilities, Carrying Amount	62,217	77,968	85,803
Derivative Liability, Fair Value, Gross Liability	62,217	77,968	85,803
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	3,213	3,241	3,340
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 [Member]
Financial assets:
Cash and due from banks, Fair Value	909,490	258,014	337,935
Available-for-sale Securities, Fair Value Disclosure	3,083,667	2,868,069	3,164,929
Held-to-maturity Securities, Fair Value Disclosure	2,487,071	630,799	355,120
Other Investments, Fair Value	267,565	140,717	140,742
Loans Held-for-sale, Fair Value Disclosure	22,855	23,683	19,018
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	43,727
Derivative Asset, Fair Value, Gross Asset	53,158	63,231	66,619
Financial liabilities:
Deposits, Fair Value	19,125,843	11,765,873	11,625,406
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	844,871	1,104,525	896,910
Other Borrowings, Fair Value	205,210	143,029	186,458
Long-term Debt, Fair Value	322,322
Accrued interest payable, Fair Value		2,515	3,266
Derivative Liability, Fair Value, Gross Liability	62,217	77,968	85,803
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	212,512	49,661	48,096
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	8,984,845	8,604,872	7,677,176
Net covered loans and loss share receivable, Fair Value	711,367	975,870	1,229,282
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 [Member]
Financial assets:
Net noncovered loans, Fair Value	4,258,892
Acquired Loans [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets:
Net noncovered loans, Fair Value	0
Acquired Loans [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets:
Net noncovered loans, Fair Value	0
Acquired Loans [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets:
Net noncovered loans, Fair Value	$ 4,258,892