Note 8 - Loans (Details) - Aging of Loan Portfolio - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Type of Loans:
Loans past due	$ 85,536	$ 112,401
Non-accrual loans	71,241	70,163
Loans not past due	9,954,396	8,801,679
Loans	10,039,932	8,914,080
Financing Receivables, 30 to 59 Days Past Due [Member]
Type of Loans:
Loans past due	7,074	36,359
Financing Receivables, 60 to 89 Days Past Due [Member]
Type of Loans:
Loans past due	4,648	5,879
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Type of Loans:
Loans past due	2,573
Commercial Portfolio Segment [Member]
Type of Loans:
Loans past due	24,519	19,816
Non-accrual loans	14,758	6,983
Loans not past due	2,337,540	2,362,677
Loans	2,362,059	2,382,493
Commercial Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Type of Loans:
Loans past due	5,865	11,595
Commercial Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Type of Loans:
Loans past due	3,896	1,238
Real Estate Construction Portfolio Segment [Member]
Type of Loans:
Loans past due	16,579	21,379
Non-accrual loans	16,579	19,963
Loans not past due	388,699	277,275
Loans	405,278	298,654
Real Estate Construction Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Type of Loans:
Loans past due		1,416
Commercial Real Estate Portfolio Segment [Member]
Type of Loans:
Loans past due	37,142	57,169
Non-accrual loans	33,214	35,606
Loans not past due	5,238,428	4,429,274
Loans	5,275,570	4,486,443
Commercial Real Estate Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Type of Loans:
Loans past due	1,114	17,654
Commercial Real Estate Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Type of Loans:
Loans past due	241	3,909
Commercial Real Estate Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Type of Loans:
Loans past due	2,573
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Type of Loans:
Loans past due	7,296	13,977
Non-accrual loans	6,690	7,611
Loans not past due	1,983,958	1,728,961
Loans	1,991,254	1,742,938
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Type of Loans:
Loans past due	95	5,634
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Type of Loans:
Loans past due	511	732
Consumer Portfolio Segment [Member]
Type of Loans:
Loans past due		60
Loans not past due	5,771	3,492
Loans	$ 5,771	3,552
Consumer Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Type of Loans:
Loans past due		$ 60