Loans and Leases (Details) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	$ 4,985,923,000			$ 4,985,923,000		$ 4,572,888,000
Originated, Weighted Average Coupon (as a percent)				4.34%		4.38%
Acquired loans	346,377,000			$ 346,377,000		$ 422,652,000
Acquired, Weighted Average Coupon (as a percent)				4.24%		4.18%
Total Loans and Leases	5,332,300,000			$ 5,332,300,000		$ 4,995,540,000
Total, Weighted Average Coupon (as a percent)				4.33%		4.36%
Unamortized deferred loan origination fees and costs	13,900,000			$ 13,900,000		$ 12,800,000
Percentage of loans to aggregate outstanding amount in the greater New York/New Jersey metropolitan area				31.30%		32.80%
Percentage of loans to aggregate outstanding amount in other areas of the United States				68.70%		67.20%
Proceeds from sale of loan portfolio				$ 37,516,000	$ 24,984,000
Loss on sale of loans	(588,000)	$ (446,000)		(1,986,000)	$ (1,594,000)
Commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	2,694,261,000			$ 2,694,261,000		$ 2,435,155,000
Originated, Weighted Average Coupon (as a percent)				3.89%		3.96%
Acquired loans	189,167,000			$ 189,167,000		$ 229,239,000
Acquired, Weighted Average Coupon (as a percent)				4.24%		4.19%
Total Loans and Leases	2,883,428,000			$ 2,883,428,000		$ 2,664,394,000
Total, Weighted Average Coupon (as a percent)				3.91%		3.98%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	1,880,163,000			$ 1,880,163,000		$ 1,684,548,000
Originated, Weighted Average Coupon (as a percent)				3.94%		4.00%
Acquired loans	158,314,000			$ 158,314,000		$ 191,044,000
Acquired, Weighted Average Coupon (as a percent)				4.19%		4.15%
Total Loans and Leases	2,038,477,000			$ 2,038,477,000		$ 1,875,592,000
Total, Weighted Average Coupon (as a percent)				3.96%		4.02%
Multi-family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	673,108,000			$ 673,108,000		$ 620,865,000
Originated, Weighted Average Coupon (as a percent)				3.77%		3.92%
Acquired loans	30,635,000			$ 30,635,000		$ 37,615,000
Acquired, Weighted Average Coupon (as a percent)				4.52%		4.35%
Total Loans and Leases	703,743,000			$ 703,743,000		$ 658,480,000
Total, Weighted Average Coupon (as a percent)				3.81%		3.94%
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	140,990,000			$ 140,990,000		$ 129,742,000
Originated, Weighted Average Coupon (as a percent)				3.72%		3.60%
Acquired loans	218,000			$ 218,000		$ 580,000
Acquired, Weighted Average Coupon (as a percent)				3.67%		5.08%
Total Loans and Leases	141,208,000			$ 141,208,000		$ 130,322,000
Total, Weighted Average Coupon (as a percent)				3.72%		3.61%
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	1,448,647,000			$ 1,448,647,000		$ 1,349,462,000
Originated, Weighted Average Coupon (as a percent)				5.59%		5.59%
Acquired loans	22,219,000			$ 22,219,000		$ 24,834,000
Acquired, Weighted Average Coupon (as a percent)				5.43%		5.83%
Total Loans and Leases	1,470,866,000			$ 1,470,866,000		$ 1,374,296,000
Total, Weighted Average Coupon (as a percent)				5.59%		5.59%
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	636,658,000			$ 636,658,000		$ 576,599,000
Originated, Weighted Average Coupon (as a percent)				3.95%		3.90%
Acquired loans	15,658,000			$ 15,658,000		$ 15,932,000
Acquired, Weighted Average Coupon (as a percent)				5.24%		5.65%
Total Loans and Leases	652,316,000			$ 652,316,000		$ 592,531,000
Total, Weighted Average Coupon (as a percent)				3.98%		3.95%
Equipment financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	758,086,000			$ 758,086,000		$ 712,988,000
Originated, Weighted Average Coupon (as a percent)				7.06%		7.05%
Acquired loans	6,561,000			$ 6,561,000		$ 8,902,000
Acquired, Weighted Average Coupon (as a percent)				5.87%		6.14%
Total Loans and Leases	764,647,000			$ 764,647,000		$ 721,890,000
Total, Weighted Average Coupon (as a percent)				7.05%		7.04%
Condominium association
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	53,903,000			$ 53,903,000		$ 59,875,000
Originated, Weighted Average Coupon (as a percent)				4.41%		4.50%
Acquired loans	0			$ 0		$ 0
Acquired, Weighted Average Coupon (as a percent)				0.00%		0.00%
Total Loans and Leases	53,903,000			$ 53,903,000		$ 59,875,000
Total, Weighted Average Coupon (as a percent)				4.41%		4.50%
Indirect automobile loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	7,607,000			$ 7,607,000		$ 13,678,000
Originated, Weighted Average Coupon (as a percent)				5.44%		5.53%
Acquired loans	0			$ 0		$ 0
Acquired, Weighted Average Coupon (as a percent)				0.00%		0.00%
Total Loans and Leases	7,607,000			$ 7,607,000		$ 13,678,000
Total, Weighted Average Coupon (as a percent)				5.44%		5.53%
Percent of loan portfolio sold, over 90%			90.00%
Proceeds from sale of loan portfolio			$ 255,200,000
Loss on sale of loans			$ 11,800
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	835,408,000			$ 835,408,000		$ 774,593,000
Originated, Weighted Average Coupon (as a percent)				3.59%		3.57%
Acquired loans	134,991,000			$ 134,991,000		$ 168,579,000
Acquired, Weighted Average Coupon (as a percent)				4.04%		3.93%
Total Loans and Leases	970,399,000			$ 970,399,000		$ 943,172,000
Total, Weighted Average Coupon (as a percent)				3.65%		3.63%
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	540,650,000			$ 540,650,000		$ 527,846,000
Originated, Weighted Average Coupon (as a percent)				3.65%		3.64%
Acquired loans	76,415,000			$ 76,415,000		$ 88,603,000
Acquired, Weighted Average Coupon (as a percent)				3.93%		3.85%
Total Loans and Leases	617,065,000			$ 617,065,000		$ 616,449,000
Total, Weighted Average Coupon (as a percent)				3.68%		3.67%
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	282,504,000			$ 282,504,000		$ 234,708,000
Originated, Weighted Average Coupon (as a percent)				3.42%		3.35%
Acquired loans	58,450,000			$ 58,450,000		$ 79,845,000
Acquired, Weighted Average Coupon (as a percent)				4.15%		3.99%
Total Loans and Leases	340,954,000			$ 340,954,000		$ 314,553,000
Total, Weighted Average Coupon (as a percent)				3.54%		3.51%
Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Originated loans	12,254,000			$ 12,254,000		$ 12,039,000
Originated, Weighted Average Coupon (as a percent)				5.15%		4.77%
Acquired loans	126,000			$ 126,000		$ 131,000
Acquired, Weighted Average Coupon (as a percent)				17.85%		17.40%
Total Loans and Leases	$ 12,380,000			$ 12,380,000		$ 12,170,000
Total, Weighted Average Coupon (as a percent)				5.28%		4.91%