CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - 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 ESOP [Member]	Unearned Equity Awards [Member]	Common Stock Held by BMP [Member]	Treasury Stock, at Cost [Member]	Total
Balance at Dec. 31, 2014	$ 529	$ 254,358	$ 427,126	$ (8,547)	$ (2,545)	$ (3,066)	$ (9,164)	$ (198,966)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised	0	149
Excess tax benefit related to stock benefit plans		(27)
Award distribution							0
Amortization of excess fair value over cost - ESOP stock and stock options expense		270
Release from treasury stock for equity awards, net of return of shares to treasury for forfeited shares		0				0	0	0
Net income			11,778						$ 11,778
Cash dividends declared and paid			(5,041)
Other comprehensive (loss) income recognized during the period, net of tax				(1,050)					1,050
Amortization of earned portion of ESOP stock					58
Amortization of earned portion of restricted stock awards						494
Treasury shares repurchased									(300)
Balance at Mar. 31, 2015	529	254,750	433,863	(9,597)	(2,487)	(2,572)	(9,164)	(199,266)	466,056
Balance at Dec. 31, 2015	533	262,798	451,606	(8,801)	(2,313)	(2,271)	(9,354)	(198,251)	493,947
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised	0	0
Excess tax benefit related to stock benefit plans		0
Award distribution							1
Amortization of excess fair value over cost - ESOP stock and stock options expense		273
Release from treasury stock for equity awards, net of return of shares to treasury for forfeited shares		135				(446)	0	338
Net income			50,037						50,037
Cash dividends declared and paid			(5,125)
Other comprehensive (loss) income recognized during the period, net of tax				252					(252)
Amortization of earned portion of ESOP stock					57
Amortization of earned portion of restricted stock awards						438
Treasury shares repurchased								0	0
Balance at Mar. 31, 2016	$ 533	$ 263,206	$ 496,518	$ (8,549)	$ (2,256)	$ (2,279)	$ (9,353)	$ (197,913)	$ 539,907