Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Loans	$ 136,133	$ 127,591	$ 120,340
Mortgage-backed securities	19,710	12,987	9,174
Other securities	6,331	4,112	1,310
FHLB of New York dividends	1,618	1,683	1,461
Deposits in other financial institutions	1,351	919	584
Total interest income	165,143	147,292	132,869
Interest expense:
Deposits	41,328	27,741	16,386
Borrowings	12,030	8,309	7,590
Total interest expense	53,358	36,050	23,976
Net interest income	111,785	111,242	108,893
Provision for loan losses	22	2,615	1,411
Net interest income after provision for loan losses	111,763	108,627	107,482
Non-interest income:
Fees and service charges for customer services	4,881	4,877	4,702
Income on bank owned life insurance	7,023	3,705	5,386
Gains on available-for-sale debt securities, net	514	178	169
Gains (losses) on trading securities, net	1,988	(879)	1,114
Other	402	246	271
Total non-interest income	14,808	8,127	11,642
Non-interest expense:
Compensation and employee benefits	39,571	34,802	38,237
Occupancy	13,676	12,096	11,270
Furniture and equipment	1,085	1,004	1,141
Data processing	5,679	5,011	4,585
Professional fees	3,545	3,482	2,774
Advertising	3,442	2,726	1,861
Federal Deposit Insurance Corporation (FDIC) insurance	563	1,065	1,064
Other	5,988	6,857	6,446
Total non-interest expense	73,549	67,043	67,378
Income before income tax expense	53,022	49,711	51,746
Income tax expense	12,787	9,632	26,978
Net income	$ 40,235	$ 40,079	$ 24,768
Net income per common share:
Basic (dollars per share)	$ 0.86	$ 0.87	$ 0.55
Diluted (dollars per share)	$ 0.85	$ 0.85	$ 0.53
Basic weighted average shares outstanding (in shares)	46,783,442	46,319,760	45,325,445
Diluted weighted average shares outstanding (in shares)	47,163,804	47,107,433	46,875,730
Net income	$ 40,235	$ 40,079	$ 24,768
Unrealized gains (losses) on debt securities available-for-sale:
Net unrealized holding gains (losses)	19,666	(5,203)	(283)
Less: reclassification adjustment for net gains included in net income	(514)	(178)	(169)
Net unrealized gains (losses)	19,152	(5,381)	(452)
Post-retirement benefits adjustment	77	240	74
Other comprehensive income (loss), before tax	19,229	(5,141)	(378)
Income tax (expense) benefit related to net unrealized holding gains (losses) on debt securities available-for-sale	(5,505)	1,462	113
Income tax benefit related to reclassification adjustment for gains included in net income	144	50	68
Income tax expense related to post-retirement benefits adjustment	(22)	(67)	(30)
Other comprehensive income (loss), net of tax	13,846	(3,696)	(227)
Comprehensive income	$ 54,081	$ 36,383	$ 24,541