Note 10 - Fair Value of Financial Instruments - Carrying Amounts and Estimated Fair Values of Selected Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Securities held-to-maturity, fair value	$ 34,152	$ 35,408
Mortgage-backed securities	537,905	516,476
Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	3,040	3,386
Interest rate swaps	3,040	3,386
Reported Value Measurement [Member]
Cash and due from banks	51,215	35,857
Securities held-to-maturity, fair value	36,406	37,735
Mortgage-backed securities	537,905	516,476
Other securities	346,238	344,905
Loans	4,974,591	4,835,693
FHLB-NY stock	57,384	59,173
Accrued interest receivable	20,602
Total assets	6,031,174	5,836,189
Deposits	4,410,746	4,205,631
Borrowings	1,227,852	1,266,563
Accrued interest payable	3,074
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,644,712	5,475,580
Reported Value Measurement [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	6,833	6,350
Interest rate swaps	3,040	3,386
Estimate of Fair Value Measurement [Member]
Cash and due from banks	51,215	35,857
Securities held-to-maturity, fair value	34,152	35,408
Mortgage-backed securities	537,905	516,476
Other securities	346,238	344,905
Loans	4,956,089	4,814,840
FHLB-NY stock	57,384	59,173
Accrued interest receivable	20,602
Total assets	6,010,418	5,813,009
Deposits	4,417,356	4,213,714
Borrowings	1,221,367	1,255,283
Accrued interest payable	3,074
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,644,837	5,472,383
Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	6,833	6,350
Interest rate swaps	3,040	3,386
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	51,215	35,857
Securities held-to-maturity, fair value
Mortgage-backed securities
Other securities
Loans
FHLB-NY stock
Accrued interest receivable
Total assets	51,215	35,857
Deposits	2,998,927	2,833,516
Borrowings
Accrued interest payable
Financial and Nonfinancial Liabilities, Fair Value Disclosure	2,998,927	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
Securities held-to-maturity, fair value
Mortgage-backed securities	537,905	516,476
Other securities	338,844	337,544
Loans
FHLB-NY stock	57,384	59,173
Accrued interest receivable	20,602
Total assets	961,568	919,543
Deposits	1,418,429	1,380,198
Borrowings	1,186,831	1,221,324
Accrued interest payable	3,074
Financial and Nonfinancial Liabilities, Fair Value Disclosure	2,611,374	2,604,908
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	6,833	6,350
Interest rate swaps	3,040	3,386
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and due from banks
Securities held-to-maturity, fair value	34,152	35,408
Mortgage-backed securities
Other securities	7,394	7,361
Loans	4,956,089	4,814,840
FHLB-NY stock
Accrued interest receivable
Total assets	4,997,635	4,857,609
Deposits
Borrowings	34,536	33,959
Accrued interest payable
Financial and Nonfinancial Liabilities, Fair Value Disclosure	34,536	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