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]		Unearned Stock Award Common Stock [Member]	Common Stock Held by BMP [Member]	Treasury Stock, at Cost [Member]	Total
Balance at Dec. 31, 2016	$ 536	$ 278,356	$ 503,539	$ (5,939)		$ (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	11,157
Other comprehensive income (loss), net of tax	0	0	0	425		0	0	0	425
Exercise of stock options, net	$ 0	624	0	0		0	0	0	624
Exercise of stock options, net (in shares)	42,062
Release of shares, net of forfeitures	$ 0	573	0	0		(1,474)	0	901	0
Release of shares, net of forfeitures (in shares)	71,433
Stock-based compensation	$ 0	0	0	0		394	0	0	394
Cash dividends declared and paid	0	0	(5,243)	0		0	0	0	(5,243)
Balance at Mar. 31, 2017	$ 536	279,553	509,453	(5,514)		(3,012)	(6,859)	(200,932)	573,225
Balance (in shares) at Mar. 31, 2017	37,569,348
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized gains and losses on available-for-sale equity securities | ASU 2016-01 [Member]	$ 0	0	153	(153)	[1]	0	0	0	0
Balance at Dec. 31, 2017	536	276,730	535,130	(3,641)		(2,894)	(2,736)	(204,558)	598,567
Balance (ASU 2016-01 [Member]) at Dec. 31, 2017	$ 536	276,730	535,283	(3,794)		(2,894)	(2,736)	(204,558)	598,567
Balance (in shares) at Dec. 31, 2017	37,419,070
Balance (in shares) (ASU 2016-01 [Member]) at Dec. 31, 2017	37,419,070
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	14,745	0		0	0	0	14,745
Other comprehensive income (loss), net of tax	0	0	0	(275)		0	0	0	(275)
Exercise of stock options, net	$ 1	454	0	0		0	0	(165)	290
Exercise of stock options, net (in shares)	19,726
Release of shares, net of forfeitures	$ 0	426	0	0		(1,349)	0	923	0
Release of shares, net of forfeitures (in shares)	73,019
Stock-based compensation	$ 0	0	0	0		388	0	0	388
Shares received to satisfy distribution of retirement benefits	$ 0	(540)	0	0		0	540	(524)	(524)
Shares received to satisfy distribution of retirement benefits (in shares)	(27,545)
Reclassification of tax effects on other comprehensive income (loss)	$ 0	0	(32)	32		0	0	0	0
Cash dividends declared and paid	0	0	(5,234)	0		0	0	0	(5,234)
Balance at Mar. 31, 2018	$ 537	$ 277,070	$ 544,762	$ (4,037)		$ (3,855)	$ (2,196)	$ (204,324)	$ 607,957
Balance (in shares) at Mar. 31, 2018	37,484,270

[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.