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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized gains and losses on marketable 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, net	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
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									38,848
Balance at Sep. 30, 2018	$ 537	277,718	558,357	(5,734)		(4,699)	(1,509)	(221,093)	603,577
Balance (in shares) at Sep. 30, 2018	36,612,153
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	12,321	0		0	0	0	12,321
Other comprehensive income (loss), net of tax	0	0	0	(541)		0	0	0	(541)
Exercise of stock options, net	$ 0	664	0	0		0	0	0	664
Exercise of stock options, net (in shares)	37,601
Release of shares, net of forfeitures	$ 0	508	0	0		(1,373)	0	874	9
Release of shares, net of forfeitures (in shares)	70,480
Stock-based compensation	$ 0	0	0	0		407	0	0	407
Shares received to satisfy distribution of retirement benefits	$ 0	(48)	0	0		0	48	(20)	(20)
Shares received to satisfy distribution of retirement benefits (in shares)	(1,090)
Cash dividends declared and paid, net	$ 0	0	(5,265)	0		0	0	0	(5,265)
Balance at Jun. 30, 2018	$ 537	278,194	551,818	(4,578)		(4,821)	(2,148)	(203,470)	615,532
Balance (in shares) at Jun. 30, 2018	37,591,261
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	11,782	0		0	0	0	11,782
Other comprehensive income (loss), net of tax	0	0	0	(1,156)		0	0	0	(1,156)
Release of shares, net of forfeitures	$ 0	88	0	0		(281)	0	197	4
Release of shares, net of forfeitures (in shares)	15,352
Stock-based compensation	$ 0	0	0	0		403	0	0	403
Shares received to satisfy distribution of retirement benefits	$ 0	(564)	0	0		0	639	(414)	(339)
Shares received to satisfy distribution of retirement benefits (in shares)	(21,260)
Cash dividends declared and paid, net	$ 0	0	(5,243)	0		0	0	0	(5,243)
Repurchase of shares of Common Stock	0	0	0	0		0	0	$ (17,406)	(17,406)
Repurchase of shares of Common Stock (in shares)								(973,200)
Balance at Sep. 30, 2018	$ 537	277,718	558,357	(5,734)		(4,699)	(1,509)	$ (221,093)	603,577
Balance (in shares) at Sep. 30, 2018	36,612,153
Balance at Dec. 31, 2018	$ 537	277,512	565,713	(6,500)		(3,623)	(1,509)	(230,049)	$ 602,081
Balance (in shares) at Dec. 31, 2018	36,081,455								36,081,455
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	11,501	0		0	0	0	$ 11,501
Other comprehensive income (loss), net of tax	0	0	0	1,268		0	0	0	1,268
Release of shares, net of forfeitures	$ 0	846	0	0		(2,729)	0	1,883	0
Release of shares, net of forfeitures (in shares)	138,329
Stock-based compensation	$ 0	0	0	0		284	0	0	284
Shares received to satisfy distribution of retirement benefits	$ 0	0	0	0		0	0	(7)	(7)
Shares received to satisfy distribution of retirement benefits (in shares)	(418)
Cash dividends declared and paid, net	$ 0	0	(5,039)	0		0	0	0	(5,039)
Repurchase of shares of Common Stock	0	0	0	0		0	0	$ (3,814)	(3,814)
Repurchase of shares of Common Stock (in shares)								(199,254)
Balance at Mar. 31, 2019	$ 537	278,358	572,175	(5,232)		(6,068)	(1,509)	$ (231,987)	606,274
Balance (in shares) at Mar. 31, 2019	36,020,112
Balance at Dec. 31, 2018	$ 537	277,512	565,713	(6,500)		(3,623)	(1,509)	(230,049)	$ 602,081
Balance (in shares) at Dec. 31, 2018	36,081,455								36,081,455
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income									$ 29,241
Balance at Sep. 30, 2019	$ 537	279,768	579,830	(6,308)		(8,892)	(1,496)	(234,535)	$ 608,904
Balance (in shares) at Sep. 30, 2019	35,951,652								35,951,652
Balance at Mar. 31, 2019	$ 537	278,358	572,175	(5,232)		(6,068)	(1,509)	(231,987)	$ 606,274
Balance (in shares) at Mar. 31, 2019	36,020,112
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	13,035	0		0	0	0	13,035
Other comprehensive income (loss), net of tax	0	0	0	(1,056)		0	0	0	(1,056)
Exercise of stock options, net	$ 0	73	0	0		0	0	0	73
Exercise of stock options, net (in shares)	8,869
Release of shares, net of forfeitures	$ 0	896	0	0		(2,588)	0	1,747	55
Release of shares, net of forfeitures (in shares)	133,451
Stock-based compensation	$ 0	0	0	0		491	0	0	491
Shares received related to tax withholding	$ 0	0	0	0		0	0	(98)	(98)
Shares received related to tax withholding (in shares)	(4,901)
Cash dividends declared and paid, net	$ 0	0	(5,051)	0		0	0	0	(5,051)
Repurchase of shares of Common Stock	0	0	0	0		0	0	$ (5,022)	(5,022)
Repurchase of shares of Common Stock (in shares)								(270,136)
Balance at Jun. 30, 2019	$ 537	279,327	580,159	(6,288)		(8,165)	(1,509)	$ (235,360)	608,701
Balance (in shares) at Jun. 30, 2019	35,887,395
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 0	0	4,705	0		0	0	0	4,705
Other comprehensive income (loss), net of tax	0	0	0	(20)		0	0	0	(20)
Release of shares, net of forfeitures	$ 0	454	0	0		(1,301)	0	847	0
Release of shares, net of forfeitures (in shares)	64,912
Stock-based compensation	$ 0	0	0	0		574	0	0	574
Shares received related to tax withholding	$ 0	0	0	0		0	0	(18)	(18)
Shares received related to tax withholding (in shares)	(466)
Shares received to satisfy distribution of retirement benefits	$ 0	(13)	0	0		0	13	(4)	(4)
Shares received to satisfy distribution of retirement benefits (in shares)	(189)
Cash dividends declared and paid, net	$ 0	0	(5,034)	0		0	0	0	(5,034)
Balance at Sep. 30, 2019	$ 537	$ 279,768	$ 579,830	$ (6,308)		$ (8,892)	$ (1,496)	$ (234,535)	$ 608,904
Balance (in shares) at Sep. 30, 2019	35,951,652								35,951,652

[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.