Note 8 - Loans (Details) - Portfolio by Risk Rating - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 10,039,932,000	$ 8,914,080,000
Loans held for sale	0	973,000
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,586,395,000	8,483,654,000
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	217,985,000	153,589,000
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	224,422,000	274,498,000
Loans held for sale		973,000
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	11,130,000	2,339,000
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,362,059,000	2,382,493,000
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,201,557,000	2,260,474,000
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	92,219,000	47,619,000
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	67,025,000	72,561,000
Commercial Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,258,000	1,839,000
Real Estate Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	405,278,000	298,654,000
Real Estate Construction Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	381,972,000	272,927,000
Real Estate Construction Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,014,000
Real Estate Construction Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	21,792,000	25,227,000
Real Estate Construction Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	500,000	500,000
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,275,570,000	4,486,443,000
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,015,411,000	4,213,453,000
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	124,350,000	105,970,000
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	126,437,000	167,020,000
Commercial Real Estate Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,372,000
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,991,254,000	1,742,938,000
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,981,684,000	1,733,248,000
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	402,000
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,168,000	9,690,000
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,771,000	3,552,000
Consumer Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 5,771,000	$ 3,552,000