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	50,037	0	0	0	0	0	50,037
Other comprehensive income (loss), net of tax	0	0	0	252	0	0	0	0	252
Release of shares, net of forfeitures	$ 0	135	0	0	0	(446)	1	338	28
Release of shares, net of forfeitures (in shares)	27,158
Stock-based compensation	$ 0	273	0	0	57	438	0	0	768
Cash dividends declared and paid	0	0	(5,125)	0	0	0	0	0	(5,125)
Balance at Mar. 31, 2016	$ 533	263,206	496,518	(8,549)	(2,256)	(2,279)	(9,353)	(197,913)	539,907
Balance (in shares) at Mar. 31, 2016	37,399,150
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	11,157	0	0	0	0	0	11,157
Other comprehensive income (loss), net of tax	0	0	0	425	0	0	0	0	425
Exercise of stock options	$ 0	624	0	0	0	0	0	0	624
Exercise of stock options (in shares)	42,062
Release of shares, net of forfeitures	$ 0	573	0	0	0	(1,474)	0	901	0
Release of shares, net of forfeitures (in shares)	71,433
Stock-based compensation	$ 0	0	0	0	0	394	0	0	394
Cash dividends declared and paid	0	0	(5,243)	0	0	0	0	0	(5,243)
Balance at Mar. 31, 2017	$ 536	$ 279,553	$ 509,453	$ (5,514)	$ 0	$ (3,012)	$ (6,859)	$ (200,932)	$ 573,225
Balance (in shares) at Mar. 31, 2017	37,569,348