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 Restricted Stock Award Common Stock [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	3	4,053
Excess tax benefit related to stock benefit plans		204
Award distribution							0
Amortization of excess fair value over cost - ESOP stock and stock options expense		541
Release from treasury stock for equity awards, net of return of shares to treasury for forfeited shares		481				(1,084)	(190)	1,006
Net income for the period			23,307						$ 23,307
Cash dividends declared and paid			(10,098)
Other comprehensive loss recognized during the period, net of tax				(802)					(802)
Amortization of earned portion of ESOP stock					116
Amortization of earned portion of restricted stock awards						985
Treasury shares repurchased (20,000 shares during the six months ended June 30, 2015)								(300)	(300)
Balance at Jun. 30, 2015	532	259,637	440,335	(9,349)	(2,429)	(3,165)	(9,354)	(198,260)	477,947
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	2	2,756
Excess tax benefit related to stock benefit plans		142
Award distribution							1
Amortization of excess fair value over cost - ESOP stock and stock options expense		561
Release from treasury stock for equity awards, net of return of shares to treasury for forfeited shares		727				(1,311)	(223)	1,105
Net income for the period			61,245						61,245
Cash dividends declared and paid			(10,282)
Other comprehensive loss recognized during the period, net of tax				(2)					(2)
Amortization of earned portion of ESOP stock					115
Amortization of earned portion of restricted stock awards						828
Treasury shares repurchased (20,000 shares during the six months ended June 30, 2015)								0	0
Balance at Jun. 30, 2016	$ 535	$ 266,984	$ 502,569	$ (8,803)	$ (2,198)	$ (2,754)	$ (9,576)	$ (197,146)	$ 549,611