Fair Value Measurement (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended			12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011		Dec. 31, 2011		Mar. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate fair value	$ 19,018	$ 22,951		$ 30,077
Contractual balance	18,267	22,419		28,948
Gain	751	532	[1]	1,129	[1]
Financial assets:
Cash and due from banks, carrying value	337,935	224,078		377,319		224,078	523,113
Available for sale securities, carrying value	3,216,365	3,498,272		3,353,553
Available for sale securities, fair value		3,498,272		3,353,553
Held to maturity Securities	352,221	80,857		82,764
Held-to-maturity Securities, Fair Value		82,905		85,112
Other securities	140,742	160,805		140,726
Loans held for sale	19,018	22,951		30,077
Net noncovered loans	7,996,079	7,299,032		7,641,245
Net covered loans and loss share receivable	1,229,282	1,721,747		1,460,723
Accrued interest receivable	43,727	42,276		42,274
Derivatives	65,418	47,809		62,056
Financial liabilities:
Deposits	11,615,841	11,340,939		11,431,609
Total Federal funds purchased and securities sold under agreements to repurchase	896,910	809,570		866,265
Wholesale borrowings	178,135	325,133		203,462
Accrued interest payable	3,266	5,851		3,915
Derivatives	84,602	72,037		86,106
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	352,221	80,857		82,764
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets:
Cash and due from banks, carrying value		224,078		377,319
Cash and due from banks, fair value	337,935
Available for sale securities, fair value	3,216,365	3,498,272		3,353,553
Held to maturity Securities	355,120	82,905		85,112
Other securities	140,742	160,805		140,726
Loans held for sale	19,018	22,951		30,077
Net noncovered loans	7,677,176	6,929,941		7,373,801
Net covered loans and loss share receivable	1,229,282	1,721,747		1,460,723
Accrued interest receivable	43,727	42,276		42,274
Derivatives	65,418	47,809		62,056
Financial liabilities:
Deposits	11,625,406	11,359,102		11,445,777
Total Federal funds purchased and securities sold under agreements to repurchase	896,910	814,030		866,265
Wholesale borrowings	186,458	328,808		211,623
Accrued interest payable	3,266	5,851		3,915
Derivatives	84,602	72,037		86,106
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial assets:
Cash and due from banks, carrying value		0
Available for sale securities, fair value	3,340	3,752		3,299
Held to maturity Securities		0
Other securities		0
Loans held for sale		0		0
Net noncovered loans		0
Net covered loans and loss share receivable		0
Accrued interest receivable		0
Financial liabilities:
Deposits		0
Total Federal funds purchased and securities sold under agreements to repurchase		0
Wholesale borrowings		0
Accrued interest payable		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial assets:
Cash and due from banks, carrying value		224,078		377,319
Cash and due from banks, fair value	337,935
Available for sale securities, fair value	3,164,929	3,349,950		3,262,715
Held to maturity Securities		82,905					85,112
Held-to-maturity Securities, Fair Value	355,120
Loans held for sale	19,018	22,951		30,077
Net noncovered loans		0
Net covered loans and loss share receivable		0
Accrued interest receivable	43,727	42,276		42,274
Derivatives	65,418	47,809		62,056
Financial liabilities:
Deposits	11,625,406	11,359,102		11,445,777
Total Federal funds purchased and securities sold under agreements to repurchase	896,910	814,030		866,265
Wholesale borrowings	186,458	328,808		211,623
Accrued interest payable	3,266	5,851		3,915
Derivatives	84,602	72,037		86,106
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial assets:
Cash and due from banks, carrying value		0
Available for sale securities, fair value	48,096	144,570		87,539
Held to maturity Securities		0
Other securities		0
Loans held for sale		0		0
Net noncovered loans	7,677,176	6,929,941		7,373,801
Net covered loans and loss share receivable	1,229,282	1,721,747		1,460,723
Accrued interest receivable		0
Financial liabilities:
Deposits		0
Total Federal funds purchased and securities sold under agreements to repurchase		0
Wholesale borrowings		0
Accrued interest payable		$ 0

[1] Included in loan sales and servicing income.