Note 6 - Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Detail) - Credit Quality Indicators by Class, Excluding Covered Loans (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Pass [Member] | Commercial And Industrial [Member]
Financing receivable - by credit quality indicators	$ 1,534,695		$ 1,308,812
Pass [Member] | Agricultural [Member]
Financing receivable - by credit quality indicators	256,772		232,270
Pass [Member] | Office Retail And Industrial [Member]
Financing receivable - by credit quality indicators	1,232,427		1,147,026
Pass [Member] | Multi-Family [Member]
Financing receivable - by credit quality indicators	305,827		275,031
Pass [Member] | Residential Construction [Member]
Financing receivable - by credit quality indicators	34,954		48,806
Pass [Member] | Commercial Construction [Member]
Financing receivable - by credit quality indicators	106,726		92,568
Pass [Member] | Other Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	714,296		746,213
Pass [Member] | Total Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	2,394,230		2,309,644
Pass [Member] | Total Corporate Loans [Member]
Financing receivable - by credit quality indicators	4,185,697		3,850,726
Special Mention [Member] | Commercial And Industrial [Member]
Financing receivable - by credit quality indicators	39,966	[1]	57,866	[1]
Special Mention [Member] | Agricultural [Member]
Financing receivable - by credit quality indicators	1,811	[1]	10,487	[1]
Special Mention [Member] | Office Retail And Industrial [Member]
Financing receivable - by credit quality indicators	58,325	[1]	78,578	[1]
Special Mention [Member] | Multi-Family [Member]
Financing receivable - by credit quality indicators	1,654	[1]	5,803	[1]
Special Mention [Member] | Residential Construction [Member]
Financing receivable - by credit quality indicators	13,867	[1]	27,198	[1]
Special Mention [Member] | Commercial Construction [Member]
Financing receivable - by credit quality indicators	14,318	[1]	23,587	[1]
Special Mention [Member] | Other Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	14,725	[1]	73,058	[1]
Special Mention [Member] | Total Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	102,889	[1]	208,224	[1]
Special Mention [Member] | Total Corporate Loans [Member]
Financing receivable - by credit quality indicators	144,666	[1]	276,577	[1]
Substandard [Member] | Commercial And Industrial [Member]
Financing receivable - by credit quality indicators	4,406	[2]	47,616	[2]
Substandard [Member] | Agricultural [Member]
Financing receivable - by credit quality indicators		[2]		[2]
Substandard [Member] | Office Retail And Industrial [Member]
Financing receivable - by credit quality indicators	16,955	[2]	43,435	[2]
Substandard [Member] | Multi-Family [Member]
Financing receivable - by credit quality indicators		[2]	1,015	[2]
Substandard [Member] | Residential Construction [Member]
Financing receivable - by credit quality indicators	8,349	[2]	11,756	[2]
Substandard [Member] | Commercial Construction [Member]
Financing receivable - by credit quality indicators	11,042	[2]	5,407	[2]
Substandard [Member] | Other Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	30,407	[2]	17,428	[2]
Substandard [Member] | Total Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	66,753	[2]	79,041	[2]
Substandard [Member] | Total Corporate Loans [Member]
Financing receivable - by credit quality indicators	71,159	[2]	126,657	[2]
Substandard Non-Accrual [Member] | Commercial And Industrial [Member]
Financing receivable - by credit quality indicators	31,102	[3]	44,152	[3]
Substandard Non-Accrual [Member] | Agricultural [Member]
Financing receivable - by credit quality indicators	1,204	[3]	1,019	[3]
Substandard Non-Accrual [Member] | Office Retail And Industrial [Member]
Financing receivable - by credit quality indicators	22,624	[3]	30,043	[3]
Substandard Non-Accrual [Member] | Multi-Family [Member]
Financing receivable - by credit quality indicators	2,028	[3]	6,487	[3]
Substandard Non-Accrual [Member] | Residential Construction [Member]
Financing receivable - by credit quality indicators	4,750	[3]	18,076	[3]
Substandard Non-Accrual [Member] | Commercial Construction [Member]
Financing receivable - by credit quality indicators	4,423	[3]	23,347	[3]
Substandard Non-Accrual [Member] | Other Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	21,284	[3]	51,447	[3]
Substandard Non-Accrual [Member] | Total Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	55,109	[3]	129,400	[3]
Substandard Non-Accrual [Member] | Total Corporate Loans [Member]
Financing receivable - by credit quality indicators	87,415	[3]	174,571	[3]
Total [Member] | Commercial And Industrial [Member]
Financing receivable - by credit quality indicators	1,610,169		1,458,446
Total [Member] | Agricultural [Member]
Financing receivable - by credit quality indicators	259,787		243,776
Total [Member] | Office Retail And Industrial [Member]
Financing receivable - by credit quality indicators	1,330,331		1,299,082
Total [Member] | Multi-Family [Member]
Financing receivable - by credit quality indicators	309,509		288,336
Total [Member] | Residential Construction [Member]
Financing receivable - by credit quality indicators	61,920		105,836
Total [Member] | Commercial Construction [Member]
Financing receivable - by credit quality indicators	136,509		144,909
Total [Member] | Other Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	780,712		888,146
Total [Member] | Total Commercial Real Estate [Member]
Financing receivable - by credit quality indicators	2,618,981		2,726,309
Total [Member] | Total Corporate Loans [Member]
Financing receivable - by credit quality indicators	$ 4,488,937		$ 4,428,531

[1] Loans categorized as special mention exhibit potential weaknesses that require the close attention of management since these potential weaknesses may result in the deterioration of repayment prospects at some future date.

[2] Loans categorized as substandard continue to accrue interest, but exhibit a well-defined weakness or weaknesses that may jeopardize the liquidation of the debt. The loans continue to accrue interest because they are well secured and collection of principal and interest is expected within a reasonable time.

[3] ) Loans categorized as non-accrual exhibit a well-defined weakness or weaknesses that may jeopardize the liquidation of the debt and are characterized by the distinct possibility that the Company could sustain some loss if the deficiencies are not corrected. These loans were placed on non-accrual status.