CONDENSED HOLDING COMPANY ONLY FINANCIAL STATEMENTS (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS [Abstract]
Cash and due from banks		$ 147,256				$ 169,455				$ 147,256	$ 169,455
Marketable equity securities, at fair value		5,667				0				5,667	0
Investment securities available-for-sale		36,280				4,006				36,280	4,006
Trading securities		0				2,715				0	2,715
MBS available-for-sale		466,605				351,384				466,605	351,384
Other assets		42,308				46,611				42,308	46,611
Total Assets		6,320,578				6,403,460				6,320,578	6,403,460
LIABILITIES AND STOCKHOLDERS' EQUITY [Abstract]
Subordinated debt, net		113,759				113,612				113,759	113,612
Other liabilities		37,400				35,666				37,400	35,666
Stockholders' equity		602,081				598,567				602,081	598,567	$ 565,868	$ 493,947
Total Liabilities and Stockholders' Equity		6,320,578				6,403,460				6,320,578	6,403,460
CONDENSED STATEMENTS OF OPERATIONS AND OTHER COMPREHENSIVE INCOME [Abstract]
Net interest loss		37,150	$ 35,028	$ 36,134	$ 38,015	38,732	$ 38,458	$ 38,053	$ 37,487	146,326	152,730	143,486
Non-interest expense		(22,745)	(21,585)	(20,827)	(21,734)	(22,573)	(22,175)	(19,469)	(20,769)	(86,890)	(84,986)	(83,831)
Income tax credit		(3,183)	(3,547)	(4,110)	(4,587)	(15,442)	(7,230)	(7,295)	(6,889)	(15,427)	(36,856)	(60,957)
Net income		12,440	11,782	12,321	14,745	15,423	13,313	11,989	11,157	51,288	51,882	72,514
Cash flows from Operating Activities [Abstract]
Net income		12,440	$ 11,782	$ 12,321	14,745	15,423	$ 13,313	$ 11,989	11,157	51,288	51,882	72,514
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Net (gain) loss on marketable equity and trading securities										302	(169)	(83)
Loss from extinguishment of debt										0	1,272	0
Decrease (Increase) in other assets										7,089	(8,477)	(2,942)
(Decrease) Increase in other liabilities										185	(906)	1,979
Net cash provided by Operating activities										64,305	43,262	20,059
Cash flows from Investing Activities [Abstract]
Proceeds from sale of investment securities available-for-sale										0	377	0
Purchases of investment securities available-for-sale										(36,248)	(145)	(22)
Net purchases of trading securities										0	(222)	(317)
Principal collected on MBS available-for-sale										76,217	957	59
Net cash provided by (used in) Investing Activities										48,333	(332,343)	(853,652)
Cash flows from Financing Activities [Abstract]
Repayment of Trust Preferred securities										0	(70,680)	0
Proceeds from Subordinated debt issuance, net										0	113,531	0
Treasury shares repurchased										(25,881)	0	0
Equity award distribution										76	236	287
BMP ESOP shares received to satisfy distribution of retirement benefits										(883)	(3,905)	(1,820)
Cash dividends paid to stockholders										(20,826)	(21,004)	(20,581)
Net cash provided by (used in) Financing Activities										(134,837)	345,033	882,942
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										(22,199)	55,952	49,349
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD					169,455				113,503	169,455	113,503	64,154
CASH AND CASH EQUIVALENTS, END OF PERIOD		147,256				169,455				147,256	169,455	113,503
Holding Company [Member]
ASSETS [Abstract]
Cash and due from banks		20,467				58,723				20,467	58,723
Marketable equity securities, at fair value		5,667				0				5,667	0
Investment securities available-for-sale		0				4,006				0	4,006
Trading securities		0				2,715				0	2,715
MBS available-for-sale		0				321				0	321
Investment in subsidiaries		689,523				643,260				689,523	643,260
Other assets		542				3,154				542	3,154
Total Assets		716,199				712,179				716,199	712,179
LIABILITIES AND STOCKHOLDERS' EQUITY [Abstract]
Subordinated debt, net		113,759				113,612				113,759	113,612
Other liabilities		359				0				359	0
Stockholders' equity		602,081				598,567				602,081	598,567
Total Liabilities and Stockholders' Equity		716,199				712,179				716,199	712,179
CONDENSED STATEMENTS OF OPERATIONS AND OTHER COMPREHENSIVE INCOME [Abstract]
Net interest loss	[1]									(5,151)	(5,427)	(4,852)
Dividends received from Bank	[1]									8,000	8,000	12,000
Non-interest income (loss)	[1]									(302)	249	478
Non-interest expense	[1]									(814)	(2,002)	(668)
Income before income taxes and equity in undistributed earnings of direct subsidiaries	[1]									1,733	820	6,958
Income tax credit	[1]									2,021	3,274	2,251
Income before equity in undistributed earnings of direct subsidiaries	[1]									3,754	4,094	9,209
Equity in undistributed earnings of subsidiaries	[1]									47,534	47,788	63,305
Net income	[1]									51,288	51,882	72,514
Cash flows from Operating Activities [Abstract]
Net income	[1]									51,288	51,882	72,514
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Equity in undistributed earnings of direct subsidiaries										(47,534)	(47,788)	(63,305)
Net (gain) loss on marketable equity and trading securities										302	(169)	(83)
Net accretion										147	81	0
Loss from extinguishment of debt										0	1,272	0
Decrease (Increase) in other assets										2,621	1,442	(2,206)
(Decrease) Increase in other liabilities										359	(994)	(7)
Net cash provided by Operating activities										7,183	5,726	6,913
Cash flows from Investing Activities [Abstract]
Proceeds from sale of investment securities available-for-sale										274	377	0
Proceeds from the sale of marketable equity and trading securities										1,059	4,629	3,648
Purchases of investment securities available-for-sale										(311)	(145)	(22)
Reimbursement from subsidiary, including purchases of investment securities available-for-sale										44	175	303
Net purchases of trading securities										0	(222)	(317)
Principal collected on MBS available-for-sale										42	49	59
Principal repayments on ESOP loan										0	0	209
Net cash provided by (used in) Investing Activities										1,108	4,863	3,880
Cash flows from Financing Activities [Abstract]
Redemption of preferred stock										0	(1)	0
Common Stock issued for exercise of stock options										954	792	3,669
Repayment of Trust Preferred securities										0	(70,680)	0
Proceeds from Subordinated debt issuance, net										0	113,531	0
Treasury shares repurchased										(25,881)	0	0
Equity award distribution										76	236	65
BMP ESOP shares received to satisfy distribution of retirement benefits										(883)	(3,905)	(1,820)
Capital contribution to subsidiary										0	(20,000)	0
Cash dividends paid to stockholders										(20,813)	(20,991)	(20,569)
Net cash provided by (used in) Financing Activities										(46,547)	(1,018)	(18,655)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										(38,256)	9,571	(7,862)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD					$ 58,723				$ 49,152	58,723	49,152	57,014
CASH AND CASH EQUIVALENTS, END OF PERIOD		$ 20,467				$ 58,723				$ 20,467	$ 58,723	$ 49,152

[1] Other comprehensive income for the Holding Company approximated other comprehensive income for the consolidated Company during the years ended December 31, 2018, 2017 and 2016.