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, 2016		52,651
Balance at Dec. 31, 2016	$ 208,410	$ 211	$ 0	$ 208,199
Net income	53,830			53,830
Stock options exercised and restricted stock awards granted (in shares)		293
Stock options exercised and restricted stock awards granted	2,259	$ 1	2,258
Share-based compensation	6,313		6,313
Stock repurchased and retired (in shares)		(522)
Stock repurchased and retired	(18,234)	$ (2)	(8,571)	(9,661)
Dividends	(13,653)			(13,653)
Balance (in shares) at Dec. 31, 2017		52,422
Balance at Dec. 31, 2017	238,925	$ 210	0	238,715
Net income	3,154
Balance at Mar. 31, 2018	242,011
Balance (in shares) at Dec. 31, 2017		52,422
Balance at Dec. 31, 2017	238,925	$ 210	0	238,715
Net income	42,329			42,329
Stock options exercised and restricted stock awards granted (in shares)		353
Stock options exercised and restricted stock awards granted	4,987	$ 1	4,986
Share-based compensation	7,862		7,862
Stock repurchased and retired (in shares)		(784)
Stock repurchased and retired	(27,943)	$ (3)	(12,848)	(15,092)
Dividends	(16,717)			(16,717)
Balance (in shares) at Dec. 31, 2018		51,991
Balance at Dec. 31, 2018	249,443	$ 208	0	249,235
Balance at Mar. 31, 2018	242,011
Net income	11,697
Balance at Jun. 30, 2018	240,833
Net income	14,514
Balance at Sep. 30, 2018	251,798
Net income	12,964
Balance (in shares) at Dec. 31, 2018		51,991
Balance at Dec. 31, 2018	249,443	$ 208	0	249,235
Net income	8,757
Balance at Mar. 31, 2019	262,546
Balance (in shares) at Dec. 31, 2018		51,991
Balance at Dec. 31, 2018	249,443	$ 208	0	249,235
Net income	53,711			53,711
Stock options exercised and restricted stock awards granted (in shares)		542
Stock options exercised and restricted stock awards granted	12,625	$ 2	12,623
Share-based compensation	11,799		11,799
Stock repurchased and retired (in shares)		(454)
Stock repurchased and retired	(20,793)	$ (2)	(20,791)	0
Dividends	(16,645)			(16,645)
Balance (in shares) at Dec. 31, 2019		52,079
Balance at Dec. 31, 2019	290,140	$ 208	3,631	286,301
Balance at Mar. 31, 2019	262,546
Net income	13,391
Balance at Jun. 30, 2019	267,511
Net income	14,290
Balance at Sep. 30, 2019	282,255
Net income	17,273
Balance (in shares) at Dec. 31, 2019		52,079
Balance at Dec. 31, 2019	$ 290,140	$ 208	$ 3,631	$ 286,301