CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 31, 2017			66,271
Beginning balance at Dec. 31, 2017	$ 168,242	$ 208	$ 7	$ 111,275	$ 56,960	$ 208
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
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
Ending balance at Dec. 31, 2018	$ 211,689		$ 7	117,763	93,919
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
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
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
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	$ 339	$ 7	123,208	122,713	$ 339
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	68,594				68,594
Dividends declared	(24,398)				(24,398)
Dividend equivalents on unvested performance-based restricted stock awards	0			141	(141)
Dividend equivalents canceled upon forfeiture of performance-based restricted stock awards	0			(84)	84
Restricted stock vestings (in shares)			299
Shares surrendered and cancelled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(99)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(2,037)			(2,037)
Repurchase of shares (in shares)			(241)
Repurchase of shares	(3,944)			(439)	(3,505)
Stock-based compensation	7,158			7,158
Issuance of common stock under employee stock purchase plan (in shares)			104
Issuance of common stock under employee stock purchase plan	$ 1,509			1,509
Ending balance (in shares) at Dec. 31, 2020	67,031		67,031
Ending balance at Dec. 31, 2020	$ 293,149		$ 7	$ 129,456	$ 163,686