CONDENSED HOLDING COMPANY ONLY FINANCIAL STATEMENTS (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS [Abstract]
Cash and due from banks		$ 169,455				$ 113,503				$ 169,455	$ 113,503
Investment securities available-for-sale		4,006				3,895				4,006	3,895
Trading securities		2,715				6,953				2,715	6,953
MBS available-for-sale		351,384				3,558				351,384	3,558
Other assets		46,611				50,063				46,611	50,063
Total assets		6,403,460				6,005,430				6,403,460	6,005,430
LIABILITIES AND STOCKHOLDERS' EQUITY [Abstract]
Trust Preferred securities payable		0				70,680				0	70,680
Subordinated debt, net		113,612				0				113,612	0
Other liabilities		35,666				39,330				35,666	39,330
Stockholders' equity		598,567				565,868				598,567	565,868	$ 493,947	$ 459,725
Total liabilities and stockholders' equity		6,403,460				6,005,430				6,403,460	6,005,430
CONDENSED STATEMENTS OF OPERATIONS AND OTHER COMPREHENSIVE INCOME [Abstract]
Net interest loss		38,732	$ 38,458	$ 38,053	$ 37,487	37,898	$ 35,347	$ 35,610	$ 34,631	152,730	143,486	128,564
Non-interest income		13,706	4,283	1,747	1,778	1,817	2,071	2,305	69,741	21,514	75,934	8,616
Non-interest expense		22,573	22,175	19,469	20,769	29,638	18,232	18,092	17,869	84,986	83,831	62,493
Income tax credit		15,442	7,230	7,295	6,889	8,816	7,481	8,173	36,487	36,856	60,957	31,245
Net income		15,423	13,313	11,989	11,157	732	10,537	11,208	50,037	51,882	72,514	44,772
Cash flows from Operating Activities [Abstract]
Net income		15,423	$ 13,313	$ 11,989	11,157	732	$ 10,537	$ 11,208	50,037	51,882	72,514	44,772
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Loss from extinguishment of debt										1,272	0	0
Decrease (Increase) in other assets										(8,477)	(2,942)	(1,464)
(Decrease) Increase in other liabilities										(906)	1,979	(430)
Net cash provided by Operating activities										43,262	20,059	50,153
Cash flows from Investing Activities [Abstract]
Proceeds from sale of investment securities available-for-sale										377	0	2,070
Proceeds from the sale of trading securities										4,629	3,648	1,340
Purchases of investment securities available-for-sale										(145)	(22)	(2,134)
Net purchases of trading securities										(222)	(317)	(3,090)
Principal collected on MBS available-for-sale										957	59	1,602
Net cash provided by (used in) Investing Activities										(332,343)	(853,652)	(553,674)
Cash flows from Financing Activities [Abstract]
Repayment of trust preferred securities										(70,680)	0	0
Proceeds from subordinated debt issuance, net										113,531	0	0
Treasury shares repurchased										0	0	(300)
Equity award distribution										236	287	251
BMP ESOP shares received to satisfy distribution of retirement benefits										(3,905)	(1,820)	0
Net cash provided by Financing Activities										345,033	882,942	489,238
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										55,952	49,349	(14,283)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD					113,503				64,154	113,503	64,154	78,437
CASH AND CASH EQUIVALENTS, END OF PERIOD		169,455				113,503				169,455	113,503	64,154
Holding Company [Member]
ASSETS [Abstract]
Cash and due from banks		58,723				49,152				58,723	49,152
Investment securities available-for-sale		4,006				3,895				4,006	3,895
Trading securities		2,715				6,953				2,715	6,953
MBS available-for-sale		321				372				321	372
Investment in subsidiaries		643,260				571,150				643,260	571,150
Other assets		3,154				6,020				3,154	6,020
Total assets		712,179				637,542				712,179	637,542
LIABILITIES AND STOCKHOLDERS' EQUITY [Abstract]
Trust Preferred securities payable		0				70,680				0	70,680
Subordinated debt, net		113,612				0				113,612	0
Other liabilities		0				994				0	994
Stockholders' equity		598,567				565,868				598,567	565,868
Total liabilities and stockholders' equity		712,179				637,542				712,179	637,542
CONDENSED STATEMENTS OF OPERATIONS AND OTHER COMPREHENSIVE INCOME [Abstract]
Net interest loss	[1]									(5,427)	(4,852)	(4,779)
Dividends received from Bank	[1]									8,000	12,000	16,000
Non-interest income	[1]									249	478	295
Non-interest expense	[1]									(2,002)	(668)	(667)
Income before income taxes and equity in undistributed earnings of direct subsidiaries	[1]									820	6,958	10,849
Income tax credit	[1]									3,274	2,251	2,321
Income before equity in undistributed earnings of direct subsidiaries	[1]									4,094	9,209	13,170
Equity in undistributed earnings of subsidiaries	[1]									47,788	63,305	31,602
Net income	[1]									51,882	72,514	44,772
Cash flows from Operating Activities [Abstract]
Net income	[1]									51,882	72,514	44,772
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Equity in undistributed earnings of direct subsidiaries										(47,788)	(63,305)	(31,602)
Net loss on the sale of investment securities available for sale										0	0	4
Net (gain) loss on trading securities										(169)	(83)	108
Net accretion										81	0	0
Loss from extinguishment of debt										1,272	0	0
Decrease (Increase) in other assets										1,442	(2,206)	(69)
(Decrease) Increase in other liabilities										(994)	(7)	(560)
Net cash provided by Operating activities										5,726	6,913	12,653
Cash flows from Investing Activities [Abstract]
Proceeds from sale of investment securities available-for-sale										377	0	2,000
Proceeds from the sale of trading securities										4,629	3,648	1,340
Purchases of investment securities available-for-sale										(145)	(22)	(2,134)
Reimbursement from subsidiary, including purchases of investment securities available-for-sale										175	303	1,655
Net purchases of trading securities										(222)	(317)	(3,090)
Principal collected on MBS available-for-sale										49	59	63
Principal repayments on ESOP loan										0	209	194
Net cash provided by (used in) Investing Activities										4,863	3,880	28
Cash flows from Financing Activities [Abstract]
Redemption of preferred stock										(1)	0	0
Common Stock issued for exercise of stock options										792	3,669	6,549
Repayment of trust preferred securities										(70,680)	0	0
Proceeds from subordinated debt issuance, net										113,531	0	0
Treasury shares repurchased										0	0	(300)
Equity award distribution										236	65	251
BMP ESOP shares received to satisfy distribution of retirement benefits										(3,905)	(1,820)	0
Capital contribution to subsidiary										(20,000)	0	0
Cash dividends paid to stockholders										(20,991)	(20,569)	(20,279)
Net cash provided by Financing Activities										(1,018)	(18,655)	(13,779)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										9,571	(7,862)	(1,098)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD					$ 49,152				$ 57,014	49,152	57,014	58,112
CASH AND CASH EQUIVALENTS, END OF PERIOD		$ 58,723				$ 49,152				$ 58,723	$ 49,152	$ 57,014

[1] Other comprehensive income for the Holding Company approximated other comprehensive income for the consolidated Company during the years ended December 31, 2017, 2016 and 2015.