CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss, Net of Deferred Taxes [Member]		Unallocated Common Stock of Employee Stock Ownership Plan ("ESOP") [Member]	Unearned Restricted Stock Award Common Stock [Member]	Common Stock Held by BMP [Member]	Treasury Stock, at Cost [Member]	Total
Balance at Dec. 31, 2015	$ 533	$ 262,798	$ 451,606	$ (8,801)		$ (2,313)	$ (2,271)	$ (9,354)	$ (198,251)	$ 493,947
Balance (in shares) at Dec. 31, 2015	37,371,992
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	72,514	0		0	0	0	0	72,514
Other comprehensive income (loss), net of tax	0	0	0	2,862		0	0	0	0	2,862
Exercise of stock options, net expired options	$ 3	3,567	0	0		0	0	0	0	3,570
Exercise of stock options, net expired options (in shares)	245,992
Release of shares, net of forfeitures	$ 0	659	0	0		0	(780)	(222)	708	365
Release of shares, net of forfeitures (in shares)	85,137
Stock-based compensation	$ 0	1,276	0	0		231	1,119	0	349	2,975
Shares received to satisfy distribution of retirement benefits	$ 0	(2,717)	0	0		0	0	2,717	(1,820)	(1,820)
Shares received to satisfy distribution of retirement benefits (in shares)	(107,008)
Tax benefit from market valuation adjustment on distribution of BMP ESOP shares	$ 0	717	0	0		0	0	0	0	717
ESOP Share Acquisition Loan payoff	$ 0	12,056	0	0		2,082	0	0	(2,819)	11,319
ESOP Share Acquisition Loan Payoff (in shares)	(140,260)
Cash dividends declared and paid	$ 0	0	(20,581)	0		0	0	0	0	(20,581)
Balance at Dec. 31, 2016	$ 536	278,356	503,539	(5,939)		0	(1,932)	(6,859)	(201,833)	565,868
Balance (in shares) at Dec. 31, 2016	37,455,853
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	51,882	0		0	0	0	0	51,882
Other comprehensive income (loss), net of tax	0	0	0	3,011		0	0	0	0	3,011
Exercise of stock options, net expired options	$ 0	792	0	0		0	0	0	0	792
Exercise of stock options, net expired options (in shares)	51,708
Release of shares, net of forfeitures	$ 0	1,269	0	0		0	(2,649)	(170)	1,786	236
Release of shares, net of forfeitures (in shares)	141,867
Stock-based compensation	$ 0	0	0	0		0	1,687	0	0	1,687
Shares received to satisfy distribution of retirement benefits	$ 0	(3,687)	0	0		0	0	4,293	(4,511)	(3,905)
Shares received to satisfy distribution of retirement benefits (in shares)	(230,358)
Reclassification of tax effects on other comprehensive income (loss)	$ 0	0	713	(713)		0	0	0	0	0
Cash dividends declared and paid	0	0	(21,004)	0		0	0	0	0	(21,004)
Balance at Dec. 31, 2017	536	276,730	535,130	(3,641)		0	(2,894)	(2,736)	(204,558)	598,567
Balance (ASU 2016-01 [Member]) at Dec. 31, 2017	$ 536	276,730	535,283	(3,794)		0	(2,894)	(2,736)	(204,558)	$ 598,567
Balance (in shares) at Dec. 31, 2017	37,419,070									37,419,070
Balance (in shares) (ASU 2016-01 [Member]) at Dec. 31, 2017	37,419,070
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized gains and losses on marketable equity securities | ASU 2016-01 [Member]	$ 0	0	153	(153)	[1]	0	0	0	0	$ 0
Net Income	0	0	51,288	0		0	0	0	0	51,288
Other comprehensive income (loss), net of tax	0	0	0	(2,738)		0	0	0	0	(2,738)
Exercise of stock options, net expired options	$ 1	1,118	0	0		0	0	0	(165)	954
Exercise of stock options, net expired options (in shares)	57,327
Release of shares, net of forfeitures	$ 0	816	0	0		0	(2,253)	0	1,513	76
Release of shares, net of forfeitures (in shares)	122,402
Stock-based compensation	$ 0	0	0	0		0	1,524	0	0	1,524
Shares received to satisfy distribution of retirement benefits	$ 0	(1,152)	0	0		0	0	1,227	(958)	(883)
Shares received to satisfy distribution of retirement benefits (in shares)	(49,895)
Reclassification of tax effects on other comprehensive income (loss)	$ 0	0	(32)	32		0	0	0	0	0
Cash dividends declared and paid	0	0	(20,826)	0		0	0	0	0	(20,826)
Repurchase of shares of Common Stock	0	0	0	0		0	0	0	$ (25,881)	(25,881)
Repurchase of shares of Common Stock (in shares)									(1,467,449)
Balance at Dec. 31, 2018	$ 537	$ 277,512	$ 565,713	$ (6,500)		$ 0	$ (3,623)	$ (1,509)	$ (230,049)	$ 602,081
Balance (in shares) at Dec. 31, 2018	36,081,455									36,081,455

[1] Represents the impact of adopting ASU 2016-01 allowing the reclassification of unrealized gains and losses on available-for-sale equity securities from accumulated other comprehensive income to Retained Earnings.