UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERSEQUITY - USD ($) $ 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	Accumulated Other Comprehensive Income
Beginning balance at Dec. 31, 2018	$ 1,425,224		$ 217	$ 1,306,653	$ 118,322		$ 32
Beginning balance, shares at Dec. 31, 2018			21,743,498
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,854			2,772	82
Exercise of stock options, net (in shares)			51,889
Exercise of stock options, net	(1,699)		$ 1	(1,700)
Issuance of restricted stock, net (in shares)			128,413
Issuance of restricted stock, net	(3,554)		$ 1	(3,555)
Common stock dividends	(11,121)				(11,121)
Unrealized gains on marketable securities, net of tax	234						234
Net income	11,500				11,500
Ending balance, shares at Mar. 31, 2019			21,923,800
Ending balance at Mar. 31, 2019	1,423,438		$ 219	1,304,170	118,783		266
Beginning balance at Dec. 31, 2019	1,462,710		$ 220	1,309,438	152,819		233
Beginning balance, shares at Dec. 31, 2019			21,964,809
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,025			3,025
Exercise of stock options, net (in shares)			14,315
Exercise of stock options, net	847		$ 0	847
Issuance of restricted stock, net (in shares)			236,232
Issuance of restricted stock, net	(25,797)		$ 2	(25,799)
Repurchase of common stock (in shares)			(1,769)
Repurchase of common stock	(247)			(105)	(142)
Common stock dividends	(13,339)				(13,339)
Unrealized gains on marketable securities, net of tax	20						20
Net income	35,239				35,239
Ending balance, shares at Mar. 31, 2020			22,213,587
Ending balance at Mar. 31, 2020	$ 1,459,147	$ (3,311)	$ 222	$ 1,287,406	$ 171,266	$ (3,311)	$ 253