Note 9 - Fair Value of Financial Instruments - Carrying Amounts and Estimated Fair Values of Selected Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Other securities	$ 29,381	$ 35,408
Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	4,740	3,386
Interest rate swaps	3,540	3,386
Reported Value Measurement [Member]
Cash and due from banks	60,161	35,857
Mortgage-backed securities	7,978
Other securities	22,952	37,735
Mortgage-backed securities	519,861	516,476
Other securities	276,698	344,905
Loans	5,070,376	4,835,693
FHLB-NY stock	55,228	59,173
Accrued interest receivable	21,076
Assets, Fair Value Disclosure	6,039,740	5,836,189
Deposits	4,444,448	4,205,631
Borrowings	1,200,682	1,266,563
Accrued interest payable	3,512
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,653,287	5,475,580
Reported Value Measurement [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	5,410	6,350
Interest rate swaps	4,645	3,386
Estimate of Fair Value Measurement [Member]
Cash and due from banks	60,161	35,857
Mortgage-backed securities	7,839
Other securities	21,542	35,408
Mortgage-backed securities	519,861	516,476
Other securities	276,698	344,905
Loans	5,058,558	4,814,840
FHLB-NY stock	55,228	59,173
Accrued interest receivable	21,076
Assets, Fair Value Disclosure	6,026,373	5,813,009
Deposits	4,445,811	4,213,714
Borrowings	1,196,962	1,255,283
Accrued interest payable	3,512
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,650,930	5,472,383
Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	5,410	6,350
Interest rate swaps	4,645	3,386
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	60,161	35,857
Mortgage-backed securities
Other securities
Mortgage-backed securities
Other securities	11,589
Loans
FHLB-NY stock
Accrued interest receivable
Assets, Fair Value Disclosure	71,750	35,857
Deposits	3,039,893	2,833,516
Borrowings
Accrued interest payable
Financial and Nonfinancial Liabilities, Fair Value Disclosure	3,039,893	2,833,516
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount
Interest rate swaps
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and due from banks
Mortgage-backed securities	7,839
Other securities
Mortgage-backed securities	519,861	516,476
Other securities	264,026	337,544
Loans
FHLB-NY stock	55,228	59,173
Accrued interest receivable	21,076
Assets, Fair Value Disclosure	873,440	919,543
Deposits	1,405,918	1,380,198
Borrowings	1,160,891	1,221,324
Accrued interest payable	3,512
Financial and Nonfinancial Liabilities, Fair Value Disclosure	2,574,966	2,604,908
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	5,410	6,350
Interest rate swaps	4,645	3,386
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and due from banks
Mortgage-backed securities
Other securities	21,542	35,408
Mortgage-backed securities
Other securities	1,083	7,361
Loans	5,058,558	4,814,840
FHLB-NY stock
Accrued interest receivable
Assets, Fair Value Disclosure	5,081,183	4,857,609
Deposits
Borrowings	36,071	33,959
Accrued interest payable
Financial and Nonfinancial Liabilities, Fair Value Disclosure	36,071	33,959
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount
Interest rate swaps