CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - 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, 2018			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 canceled upon forfeiture of performance-based restricted stock awards	0			(122)	122
Restricted stock vestings (in shares)			364
Restricted stock vestings	0
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(153)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(2,609)			(2,609)
Stock-based compensation	2,272			2,272
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 Mar. 31, 2019			66,911
Ending balance at Mar. 31, 2019	218,895		$ 7	118,774	100,114
Beginning balance (in shares) at Dec. 31, 2018			66,569
Beginning balance at Dec. 31, 2018	211,689		$ 7	117,763	93,919
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,473
Ending balance (in shares) at Sep. 30, 2019			66,961
Ending balance at Sep. 30, 2019	239,911		$ 7	121,706	118,198
Beginning balance (in shares) at Mar. 31, 2019			66,911
Beginning balance at Mar. 31, 2019	218,895		$ 7	118,774	100,114
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,460				14,460
Dividends declared	(5,416)				(5,416)
Dividend equivalents on unvested performance-based restricted stock awards	0			27	(27)
Restricted stock vestings (in shares)			47
Restricted stock vestings	0
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(2)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(28)			(28)
Stock-based compensation	1,431			1,431
Ending balance (in shares) at Jun. 30, 2019			66,956
Ending balance at Jun. 30, 2019	229,342		$ 7	120,204	109,131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,510				14,510
Dividends declared	(5,416)				(5,416)
Dividend equivalents on unvested performance-based restricted stock awards	0			27	(27)
Restricted stock vestings (in shares)			8
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(3)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(49)			(49)
Stock-based compensation	1,524			1,524	0
Ending balance (in shares) at Sep. 30, 2019			66,961
Ending balance at Sep. 30, 2019	$ 239,911		$ 7	121,706	118,198
Beginning balance (in shares) at Dec. 31, 2019	66,968		66,968
Beginning balance at Dec. 31, 2019	$ 245,928	$ 339	$ 7	123,208	122,713	$ 339
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,863				11,863
Dividends declared	(6,105)				(6,105)
Dividend equivalents on unvested performance-based restricted stock awards	0			35	(35)
Dividend equivalents canceled upon forfeiture of performance-based restricted stock awards	0			(84)	84
Restricted stock vestings (in shares)			228
Restricted stock vestings	0
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(91)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(1,865)			(1,865)
Repurchase of shares (in shares)			(241)
Repurchase of shares	(3,944)			(439)	(3,505)
Stock-based compensation	1,319			1,319
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 Mar. 31, 2020			66,968
Ending balance at Mar. 31, 2020	$ 249,044		$ 7	123,683	125,354
Beginning balance (in shares) at Dec. 31, 2019	66,968		66,968
Beginning balance at Dec. 31, 2019	$ 245,928	$ 339	$ 7	123,208	122,713	$ 339
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 50,750
Ending balance (in shares) at Sep. 30, 2020	67,026		67,026
Ending balance at Sep. 30, 2020	$ 279,342		$ 7	127,358	151,977
Beginning balance (in shares) at Mar. 31, 2020			66,968
Beginning balance at Mar. 31, 2020	249,044		$ 7	123,683	125,354
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,796				13,796
Dividends declared	(6,097)				(6,097)
Dividend equivalents on unvested performance-based restricted stock awards	0			35	(35)
Restricted stock vestings (in shares)			53
Restricted stock vestings	0
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(2)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(53)			(53)
Stock-based compensation	1,739			1,739
Ending balance (in shares) at Jun. 30, 2020			67,019
Ending balance at Jun. 30, 2020	258,429		$ 7	125,404	133,018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,091				25,091
Dividends declared	(6,097)				(6,097)
Dividend equivalents on unvested performance-based restricted stock awards	0			35	(35)
Restricted stock vestings (in shares)			11
Restricted stock vestings	0
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings (in shares)			(4)
Shares surrendered and canceled upon vesting of restricted stock to satisfy tax withholdings	(79)			(79)
Stock-based compensation	$ 1,998			1,998
Ending balance (in shares) at Sep. 30, 2020	67,026		67,026
Ending balance at Sep. 30, 2020	$ 279,342		$ 7	$ 127,358	$ 151,977