Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income
Beginning balance, shares at Dec. 31, 2017		11,167,425
Beginning balance at Dec. 31, 2017	$ 209,197	$ 112	$ 47,079	$ 162,006	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	5,937		5,937
Issuance of restricted stock, net (in shares)		139,102
Issuance of restricted stock, net		$ 1	(1)
Common stock dividends	(5,778)			(5,778)
Unrealized gains on marketable securities, net of tax	0
Net income	14,655			14,655
Ending balance, shares at Jun. 30, 2018		11,306,527
Ending balance at Jun. 30, 2018	223,840	$ 113	53,015	170,712	0
Beginning balance, shares at Mar. 31, 2018		11,300,671
Beginning balance at Mar. 31, 2018	218,292	$ 113	49,766	168,413	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,249		3,249
Issuance of restricted stock, net (in shares)		5,856
Common stock dividends	(2,889)			(2,889)
Unrealized gains on marketable securities, net of tax	0
Net income	5,188			5,188
Ending balance, shares at Jun. 30, 2018		11,306,527
Ending balance at Jun. 30, 2018	223,840	$ 113	53,015	170,712	0
Beginning balance, shares at Dec. 31, 2018		21,743,498
Beginning balance at Dec. 31, 2018	1,425,224	$ 217	1,306,653	118,322	32
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	6,008		5,926	82
Exercise of stock options, net (in shares)		90,569
Exercise of stock options, net	(208)	$ 1	(209)
Issuance of restricted stock, net (in shares)		114,496
Issuance of restricted stock, net	(7,221)	$ 1	(7,222)
Common stock dividends	(22,253)			(22,253)
Unrealized gains on marketable securities, net of tax	417				417
Net income	35,909			35,909
Ending balance, shares at Jun. 30, 2019		21,948,563
Ending balance at Jun. 30, 2019	1,437,876	$ 219	1,305,148	132,060	449
Beginning balance, shares at Mar. 31, 2019		21,923,800
Beginning balance at Mar. 31, 2019	1,423,438	$ 219	1,304,170	118,783	266
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,155		3,155
Exercise of stock options, net (in shares)		38,680
Exercise of stock options, net	1,491		1,491
Issuance of restricted stock, net (in shares)		(13,917)
Issuance of restricted stock, net	(3,668)		(3,668)
Common stock dividends	(11,132)			(11,132)
Unrealized gains on marketable securities, net of tax	183				183
Net income	24,409			24,409
Ending balance, shares at Jun. 30, 2019		21,948,563
Ending balance at Jun. 30, 2019	$ 1,437,876	$ 219	$ 1,305,148	$ 132,060	$ 449