Consolidated Statements of Changes in Shareholders' Equity (unaudited) - USD ($) $ in Thousands		Total	Restricted Stock Units (RSUs)	Dividend declared	Common Stock		Common Stock Restricted Stock Units (RSUs)	Retained Earnings	Retained Earnings Dividend paid	Retained Earnings Dividend declared	Accumulated Other Comprehensive (Loss) Gain
Balance (in shares) at Dec. 31, 2017	[1]				16,885,615
Balance at Dec. 31, 2017		$ 101,352			$ 57,880			$ 44,182			$ (710)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2016-01: reclassification of TRUPS to accumulated other comprehensive income		(1,482)
Adoption of ASU 2016-01: reclassification of TRUPS to accumulated other comprehensive income | ASU 2016-01								(1,482)			1,482
Balance (in shares) at Jan. 01, 2018					16,885,615
Balance at Jan. 01, 2018		101,352			$ 57,880			42,516			956
Balance (in shares) at Dec. 31, 2017	[1]				16,885,615
Balance at Dec. 31, 2017		101,352			$ 57,880			44,182			(710)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)		230									230
Dividends on common stock				$ (1,521)						$ (1,521)
Restricted stock units released (in shares)							13,000
Restricted stock units released			$ 0
Stock-based compensation expense		291			$ 291
Net Income		3,157						3,157
Balance (in shares) at Mar. 31, 2018	[2]				16,898,615
Balance at Mar. 31, 2018		103,509			$ 58,171			44,152			1,186
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2016-01: recognition of previously unrealized losses within marketable equity securities | ASU 2016-01								(184)			184
Other comprehensive income (loss)		(512)									(512)
Dividends on common stock		(3,211)		(1,859)					$ (3,211)	(1,859)
Restricted stock units released (in shares)							48,007
Restricted stock units released			0
Stock-based compensation expense		453			$ 453
Net Income		$ 10,860						10,860
Balance (in shares) at Dec. 31, 2018		16,946,622			16,946,622	[3]
Balance at Dec. 31, 2018		$ 109,240			$ 58,624			49,942			674
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)		(284)									(284)
Dividends on common stock				$ (1,869)						$ (1,869)
Restricted stock units released (in shares)							2,500
Restricted stock units released			$ 0
Stock-based compensation expense		99			$ 99
Net Income		$ 4,007						4,007
Balance (in shares) at Mar. 31, 2019		16,949,122			16,949,122	[4]
Balance at Mar. 31, 2019		$ 111,193			$ 58,723			$ 52,080			$ 390

[1] Excludes 46,511 unvested restricted shares

[2] Excludes 116,597 unvested restricted shares

[3] Excludes 59,217 unvested restricted shares

[4] Excludes 58,717 unvested restricted shares