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, 2011		Dec. 31, 2010
Commercial real estate:
Multi-family	$ 288,336		$ 349,862
Residential construction	105,836		174,690
Total commercial real estate	2,726,309		2,748,994
Total corporate loans	4,428,531		4,442,653
Consumer	659,582		657,907
Total loans, excluding covered loans	5,088,113		5,100,560
Individually Evaluated For Impairment [Member]
Commercial, industrial, and agricultural	37,385		43,365
Commercial real estate:
Office, retail, and industrial	28,216		18,076
Multi-family	5,589		5,696
Residential construction	17,378		51,269
Other commercial real estate	70,919		68,918
Total commercial real estate	122,102		143,959
Total corporate loans	159,487		187,324
Total loans, excluding covered loans	159,487
Covered loans (1)		[1]
Total	159,487		187,324
Collectively Evaluated For Impairment [Member]
Commercial, industrial, and agricultural	1,664,837		1,650,294
Commercial real estate:
Office, retail, and industrial	1,270,866		1,185,537
Multi-family	282,747		344,166
Residential construction	88,458		123,421
Other commercial real estate	962,136		951,911
Total commercial real estate	2,604,207		2,605,035
Total corporate loans	4,269,044		4,255,329
Consumer	659,582		657,907
Total loans, excluding covered loans	4,928,626
Covered loans (1)	45,451	[1]
Total	4,974,077		4,913,236
Loans Total [Member]
Commercial, industrial, and agricultural	1,702,222		1,693,659
Commercial real estate:
Office, retail, and industrial	1,299,082		1,203,613
Multi-family	288,336		349,862
Residential construction	105,836		174,690
Other commercial real estate	1,033,055		1,020,829
Total commercial real estate	2,726,309		2,748,994
Total corporate loans	4,428,531		4,442,653
Consumer	659,582		657,907
Total loans, excluding covered loans	5,088,113
Covered loans (1)	45,451	[1]
Total	5,133,564		5,100,560
Individually Evaluated For Impairment Allowance [Member]
Commercial, industrial, and agricultural	14,827		2,650
Commercial real estate:
Office, retail, and industrial	1,507
Multi-family	20		497
Residential construction	2,502
Other commercial real estate	7,239		3,196
Total commercial real estate	11,268		3,693
Total corporate loans	26,095		6,343
Total loans, excluding covered loans	26,095
Covered loans (1)		[1]
Total	26,095		6,343
Collectively Evaluated For Impairment Allowance [Member]
Commercial, industrial, and agricultural	31,190		46,895
Commercial real estate:
Office, retail, and industrial	14,505		20,758
Multi-family	5,047		3,499
Residential construction	12,061		27,933
Other commercial real estate	17,232		26,673
Total commercial real estate	48,845		78,863
Total corporate loans	80,035		125,758
Consumer	14,843		12,971
Total loans, excluding covered loans	94,878
Covered loans (1)	989	[1]
Total	95,867		138,729
Total Allowance [Member]
Commercial, industrial, and agricultural	46,017		49,545
Commercial real estate:
Office, retail, and industrial	16,012		20,758
Multi-family	5,067		3,996
Residential construction	14,563		27,933
Other commercial real estate	24,471		29,869
Total commercial real estate	60,113		82,556
Total corporate loans	106,130		132,101
Consumer	14,843		12,971
Total loans, excluding covered loans	120,973
Covered loans (1)	989	[1]
Total	$ 121,962		$ 145,072

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