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	23,146	0		0	0	0	23,146
Other comprehensive income (loss), net of tax	0	0	0	292		0	0	0	292
Exercise of stock options, net	$ 0	626	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		(3,339)	(170)	2,236	198
Release of shares, net of forfeitures (in shares)	177,347
Stock-based compensation	$ 0	0	0	0		838	0	0	838
Cash dividends declared and paid	0	0	(10,520)	0		0	0	0	(10,520)
Balance at Jun. 30, 2017	$ 536	280,453	516,165	(5,647)		(4,433)	(7,029)	(199,597)	580,448
Balance (in shares) at Jun. 30, 2017	37,675,379
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	27,066	0		0	0	0	27,066
Other comprehensive income (loss), net of tax	0	0	0	(816)		0	0	0	(816)
Exercise of stock options, net	$ 1	1,118	0	0		0	0	(165)	954
Exercise of stock options (in shares)	57,327
Release of shares, net of forfeitures	$ 0	934	0	0		(2,722)	0	1,797	9
Release of shares, net of forfeitures (in shares)	143,499
Stock-based compensation	$ 0	0	0	0		795	0	0	795
Shares received to satisfy distribution of retirement benefits	$ 0	(588)	0	0		0	588	(544)	(544)
Shares received to satisfy distribution of retirement benefits (in shares)	(28,635)
Reclassification of tax effects on other comprehensive income (loss)	$ 0	0	(32)	32		0	0	0	0
Cash dividends declared and paid	0	0	(10,499)	0		0	0	0	(10,499)
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

[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.