Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings
Balance (in shares) at Dec. 31, 2015		53,012
Balance at Dec. 31, 2015	$ 178,918	$ 212	$ 0	$ 178,706
Net income	53,376			53,376
Stock options exercised and restricted stock awards granted, including tax benefits (in shares)		375
Stock options exercised and restricted stock awards granted, including tax benefits	2,063	$ 2	2,061
Share-based compensation	4,357		4,357
Stock repurchased and retired (in shares)		(736)
Stock repurchased and retired	(20,140)	$ (3)	(6,418)	(13,719)
Dividends	(12,676)			(12,676)
Balance (in shares) at Dec. 31, 2016		52,651
Balance at Dec. 31, 2016	205,898	$ 211	0	205,687
Net income	54,498			54,498
Stock options exercised and restricted stock awards granted, including tax benefits (in shares)		293
Stock options exercised and restricted stock awards granted, including tax benefits	2,259	$ 1	2,258
Share-based compensation	6,458		6,458
Stock repurchased and retired (in shares)		(522)
Stock repurchased and retired	(18,234)	$ (2)	(8,716)	(9,516)
Dividends	(13,653)			(13,653)
Balance (in shares) at Dec. 31, 2017		52,422
Balance at Dec. 31, 2017	237,226	$ 210	0	237,016
Net income	42,572			42,572
Stock options exercised and restricted stock awards granted, including tax benefits (in shares)		353
Stock options exercised and restricted stock awards granted, including tax benefits	4,987	$ 1	4,986
Share-based compensation	7,374		7,374
Stock repurchased and retired (in shares)		(784)
Stock repurchased and retired	(27,943)	$ (3)	(12,360)	(15,580)
Dividends	(16,717)			(16,717)
Balance (in shares) at Dec. 31, 2018		51,991
Balance at Dec. 31, 2018	$ 247,499	$ 208	$ 0	$ 247,291