Note 6 - Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Detail) - Loans and Related Allowance for Credit Losses by Portfolio Segment (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Loans	$ 5,387,570		$ 5,348,615
Allowance for credit losses	102,812		121,962		145,072	144,808
Office Retail And Industrial [Member]
Loans individually evaluated for impairment	21,736		28,216
Loans collectively evaluated for impairment	1,311,455		1,270,866
Loans acquired with deteriorated credit quality		[1]		[1]
Loans	1,333,191		1,299,082
Allowance for credit losses individually evaluated for impairment	971		1,507
Allowance for credit losses collectively evaluated for impairment	10,461		14,505
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	11,432		16,012
Multi-Family [Member]
Loans individually evaluated for impairment	642		5,589
Loans collectively evaluated for impairment	284,718		282,747
Loans acquired with deteriorated credit quality	121	[1]		[1]
Loans	285,481		288,336
Allowance for credit losses individually evaluated for impairment			20
Allowance for credit losses collectively evaluated for impairment	3,575		5,047
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	3,575		5,067
Residential Construction [Member]
Loans individually evaluated for impairment	4,040		17,378
Loans collectively evaluated for impairment	57,422		88,458
Loans acquired with deteriorated credit quality		[1]		[1]
Loans	61,462		105,836
Allowance for credit losses individually evaluated for impairment			2,502
Allowance for credit losses collectively evaluated for impairment	6,260		12,061
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	6,260		14,563
Other Commercial Real Estate [Member]
Loans individually evaluated for impairment	16,160		70,919
Loans collectively evaluated for impairment	877,749		962,136
Loans acquired with deteriorated credit quality	4,166	[1]		[1]
Loans	898,075		1,033,055
Allowance for credit losses individually evaluated for impairment	1,247		7,239
Allowance for credit losses collectively evaluated for impairment	17,433		17,232
Allowance for credit losses acquired with deteriorated credit quality				[1]
Allowance for credit losses	18,680		24,471
Total Corporate Loans [Member]
Loans individually evaluated for impairment	66,309		159,487
Loans collectively evaluated for impairment	4,405,808		4,269,044
Loans acquired with deteriorated credit quality	6,184	[1]		[1]
Loans	4,478,301		4,428,531
Allowance for credit losses individually evaluated for impairment	11,622		26,095
Allowance for credit losses collectively evaluated for impairment	65,086		80,035
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	76,708		106,130
Consumer [Member]
Loans collectively evaluated for impairment	699,361		659,582
Loans acquired with deteriorated credit quality	12,014	[1]		[1]
Loans	711,375		659,582
Allowance for credit losses collectively evaluated for impairment	14,042		14,843
Allowance for credit losses acquired with deteriorated credit quality		[1]
Allowance for credit losses	14,042		14,843
Total Loans Excluding Covered Loans [Member]
Loans individually evaluated for impairment	66,309		159,487
Loans collectively evaluated for impairment	5,105,169		4,928,626
Loans acquired with deteriorated credit quality	18,198	[1]		[1]
Loans	5,189,676		5,088,113
Allowance for credit losses individually evaluated for impairment	11,622		26,095
Allowance for credit losses collectively evaluated for impairment	79,128		94,878
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	90,750		120,973
Covered Home Equity Lines [Member]
Loans individually evaluated for impairment		[2]
Loans collectively evaluated for impairment	43,132	[2]
Loans acquired with deteriorated credit quality		[1],[2]
Loans	43,132	[2]
Allowance for credit losses individually evaluated for impairment		[2]
Allowance for credit losses collectively evaluated for impairment	928	[2]
Allowance for credit losses acquired with deteriorated credit quality		[1],[2]
Allowance for credit losses	928	[2]
Other Covered Loans [Member]
Loans acquired with deteriorated credit quality	154,762	[1]
Loans	154,762
Allowance for credit losses acquired with deteriorated credit quality	11,134	[1]
Allowance for credit losses	11,134
Covered Loans [Member]
Loans individually evaluated for impairment				[2]
Loans collectively evaluated for impairment	43,132		45,451	[2]
Loans acquired with deteriorated credit quality	154,762	[1]		[1],[2]
Loans	197,894		45,451	[2]
Allowance for credit losses individually evaluated for impairment				[2]
Allowance for credit losses collectively evaluated for impairment	928		989	[2]
Allowance for credit losses acquired with deteriorated credit quality	11,134	[1]		[1],[2]
Allowance for credit losses	12,062		989	[2]
Total Loans Included in Calculation of Allowance [Member]
Loans individually evaluated for impairment	66,309		159,487
Loans collectively evaluated for impairment	5,148,301		4,974,077
Loans acquired with deteriorated credit quality	172,960	[1]		[1]
Loans	5,387,570		5,133,564
Allowance for credit losses individually evaluated for impairment	11,622		26,095
Allowance for credit losses collectively evaluated for impairment	80,056		95,867
Allowance for credit losses acquired with deteriorated credit quality	11,134	[1]		[1]
Allowance for credit losses	102,812		121,962
Commercial Loan [Member]
Loans individually evaluated for impairment	23,731		37,385
Loans collectively evaluated for impairment	1,874,464		1,664,837
Loans acquired with deteriorated credit quality	1,897	[1]		[1]
Loans	1,900,092		1,702,222
Allowance for credit losses individually evaluated for impairment	9,404		14,827
Allowance for credit losses collectively evaluated for impairment	27,357		31,190
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	36,761		46,017
Commercial Real Estate [Member]
Loans individually evaluated for impairment	42,578		122,102
Loans collectively evaluated for impairment	2,531,344		2,604,207
Loans acquired with deteriorated credit quality	4,287	[1]		[1]
Loans	2,578,209		2,726,309
Allowance for credit losses individually evaluated for impairment	2,218		11,268
Allowance for credit losses collectively evaluated for impairment	37,729		48,845
Allowance for credit losses acquired with deteriorated credit quality		[1]		[1]
Allowance for credit losses	$ 39,947		$ 60,113

[1] As of December 31, 2012, loans acquired with deteriorated credit quality included certain loans from the Waukegan Savings transaction and covered loans, excluding covered home equity lines. An allowance for loan losses was not recorded on the loans from the Waukegan Savings transaction as of December 31, 2012, since the Company did not re-estimate cash flows on these loans following the acquisition due to its proximity to year end. During 2012, the Company established an allowance for covered loan losses, which reflects the difference between the carrying value and the discounted present value of the estimated cash flows of the covered loans

[2] These are open-end consumer loans that are not categorized as purchased impaired loans.