Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings
Balance at Dec. 31, 2017	$ 237,226	$ 210	$ 0	$ 237,016
Balance (in shares) at Dec. 31, 2017		52,422
Net income	30,036			30,036
Stock options exercised and restricted stock awards granted	3,504	$ 1	3,503
Stock options exercised and restricted stock awards granted (in shares)		301
Share-based compensation	5,614		5,614
Stock repurchased and retired	(18,360)	$ (2)	(9,117)	(9,241)
Stock repurchased and retired (in shares)		(513)
Dividends	(8,391)			(8,391)
Balance at Sep. 30, 2018	249,629	$ 209	0	249,420
Balance (in shares) at Sep. 30, 2018		52,210
Balance at Jun. 30, 2018	238,437	$ 209	0	238,228
Balance (in shares) at Jun. 30, 2018		52,290
Net income	14,085			14,085
Stock options exercised and restricted stock awards granted	1,205		1,205
Stock options exercised and restricted stock awards granted (in shares)		75
Share-based compensation	1,915		1,915
Stock repurchased and retired	(6,013)		(3,120)	(2,893)
Stock repurchased and retired (in shares)		(155)
Balance at Sep. 30, 2018	249,629	$ 209	0	249,420
Balance (in shares) at Sep. 30, 2018		52,210
Balance at Dec. 31, 2018	247,499	$ 208	0	247,291
Balance (in shares) at Dec. 31, 2018		51,991
Net income	37,690			37,690
Stock options exercised and restricted stock awards granted	11,283	$ 2	11,281
Stock options exercised and restricted stock awards granted (in shares)		494
Share-based compensation	7,858		7,858
Stock repurchased and retired	(16,460)	$ (1)	(16,459)
Stock repurchased and retired (in shares)		(366)
Dividends	(8,303)			(8,303)
Balance at Sep. 30, 2019	279,567	$ 209	2,680	276,678
Balance (in shares) at Sep. 30, 2019		52,119
Balance at Jun. 30, 2019	264,569	$ 209	1,586	262,774
Balance (in shares) at Jun. 30, 2019		52,118
Net income	13,827			13,827
Stock options exercised and restricted stock awards granted	3,598		3,598
Stock options exercised and restricted stock awards granted (in shares)		110
Share-based compensation	2,785		2,785
Stock repurchased and retired	(5,289)		(5,289)
Stock repurchased and retired (in shares)		(109)
Dividends	77			77
Balance at Sep. 30, 2019	$ 279,567	$ 209	$ 2,680	$ 276,678
Balance (in shares) at Sep. 30, 2019		52,119