CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2016		65,982
Beginning balance at Dec. 31, 2016	$ 133,903	$ 7	$ 106,669	$ 27,227
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	51,614			51,614
Dividends declared	(21,393)			(21,393)
Dividend equivalents on unvested performance-based restricted stock awards	0		110	(110)
Dividend equivalents canceled upon forfeiture of performance-based restricted stock awards	0		(31)	31
Restricted stock vestings (in shares)		319
Restricted stock vestings	0
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings (in shares)		(122)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(2,676)		(2,676)
Stock-based compensation	5,464		5,464
Shares issuable in lieu of dividend payments on performance-based restricted stock awards (in shares)		5
Shares issuable in lieu of dividend payments on performance-based restricted stock awards	0
Issuance of common stock under employee stock purchase plan (in shares)		87
Issuance of common stock under employee stock purchase plan	1,330		1,330
Ending balance (in shares) at Dec. 31, 2017		66,271
Ending balance at Dec. 31, 2017	168,242	$ 7	111,275	56,960
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58,269			58,269
Dividends declared	(21,521)			(21,521)
Dividend equivalents on unvested performance-based restricted stock awards	0		137	(137)
Dividend equivalents canceled upon forfeiture of performance-based restricted stock awards	0		(140)	140
Restricted stock vestings (in shares)		263
Restricted stock vestings	0
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings (in shares)		(87)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(1,229)		(1,229)
Stock-based compensation	6,338		6,338
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
Ending balance (in shares) at Dec. 31, 2018	66,569	66,569
Ending balance at Dec. 31, 2018	$ 211,689	$ 7	117,763	93,919
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	50,430			50,430
Dividends declared	(21,649)			(21,649)
Dividend equivalents on unvested performance-based restricted stock awards	0		109	(109)
Dividend equivalents canceled upon forfeiture of performance-based restricted stock awards	0		(122)	122
Restricted stock vestings (in shares)		427
Restricted stock vestings	0
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings (in shares)		(159)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(2,754)		(2,754)
Stock-based compensation	6,769		6,769
Shares issuable in lieu of dividend payments on performance-based restricted stock awards (in shares)		3
Shares issuable in lieu of dividend payments on performance-based restricted stock awards	0
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 Dec. 31, 2019	66,968	66,968
Ending balance at Dec. 31, 2019	$ 245,928	$ 7	$ 123,208	$ 122,713