CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net cumulative effect of adoption of accounting standard	$ 208			$ 208
Beginning balance (in shares) at Dec. 31, 2017		66,271
Beginning balance at Dec. 31, 2017	168,242	$ 7	$ 111,275	56,960
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,508			15,508
Dividends declared	(5,370)			(5,370)
Dividend equivalents on unvested performance-based restricted stock awards	$ 0		$ 34	$ (34)
Dividend equivalents cancelled upon forfeiture of performance-based restricted stock awards	0		(140)	140
Restricted stock vestings (in shares)		202
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings (in shares)		(81)
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings	$ (1,132)		$ (1,132)
Stock-based compensation	1,511		1,511	$ 0
Issuance of common stock under employee stock purchase plan (in shares)		122
Issuance of common stock under employee stock purchase plan	1,382		1,382	0
Ending balance (in shares) at Mar. 31, 2018		66,514
Ending balance at Mar. 31, 2018	$ 180,349	$ 7	112,930	67,412
Beginning balance (in shares) at Dec. 31, 2018	66,569	66,569
Beginning balance at Dec. 31, 2018	$ 211,689	$ 7	117,763	93,919
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,502			11,502
Dividends declared	(5,402)			(5,402)
Dividend equivalents on unvested performance-based restricted stock awards	$ 0		$ 27	$ (27)
Dividend equivalents cancelled upon forfeiture of performance-based restricted stock awards	0		(122)	122
Restricted stock vestings (in shares)		364
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings (in shares)		(153)
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings	$ (2,609)		$ (2,609)
Stock-based compensation	2,272		2,272	$ 0
Shares issuable in lieu of dividend payments on performance-based restricted stock awards (in shares)		3
Issuance of common stock under employee stock purchase plan (in shares)		128
Issuance of common stock under employee stock purchase plan	$ 1,443		1,443
Ending balance (in shares) at Mar. 31, 2019	66,911	66,911
Ending balance at Mar. 31, 2019	$ 218,895	$ 7	$ 118,774	$ 100,114