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 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	61,245	0	0	0	0	0	61,245
Other comprehensive income (loss), net of tax	0	0	0	(2)	0	0	0	0	(2)
Exercise of stock options	$ 2	2,898	0	0	0	0	0	0	2,900
Exercise of stock options (in shares)	193,828
Release of shares, net of forfeitures	$ 0	727	0	0	0	(1,311)	(222)	1,105	299
Release of shares, net of forfeitures (in shares)	88,951
Stock-based compensation	$ 0	561	0	0	115	828	0	0	1,504
Cash dividends declared and paid	0	0	(10,282)	0	0	0	0	0	(10,282)
Balance at Jun. 30, 2016	$ 535	266,984	502,569	(8,803)	(2,198)	(2,754)	(9,576)	(197,146)	549,611
Balance (in shares) at Jun. 30, 2016	37,654,771
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	23,146	0	0	0	0	0	23,146
Other comprehensive income (loss), net of tax	0	0	0	292	0	0	0	0	292
Exercise of stock options	$ 0	626	0	0	0	0	0	0	626
Exercise of stock options (in shares)	42,179
Release of shares, net of forfeitures	$ 0	1,471	0	0	0	(3,339)	(170)	2,236	198
Release of shares, net of forfeitures (in shares)	177,347
Stock-based compensation	$ 0	0	0	0	0	838	0	0	838
Cash dividends declared and paid	0	0	(10,520)	0	0	0	0	0	(10,520)
Balance at Jun. 30, 2017	$ 536	$ 280,453	$ 516,165	$ (5,647)	$ 0	$ (4,433)	$ (7,029)	$ (199,597)	$ 580,448
Balance (in shares) at Jun. 30, 2017	37,675,379