CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Common Stock In Treasury	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2017	$ 530	$ (1,397,962)	$ 1,274,811	$ 1,399,495	$ (380)	$ 1,276,494
Balance (in shares) at Dec. 31, 2017	52,973	(28,771)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense			7,646			7,646
Exercise of stock options	$ 3		17,131			17,134
Exercise of stock options (in shares)	300
Issuance of equity	$ 1		(3,052)			(3,051)
Issuance of equity (in shares)	125
Net income				11,452		11,452
Other comprehensive income (loss)-other					(319)	(319)
Adoption of new accounting standards				(4,227)		(4,227)
Balance at Mar. 31, 2018	$ 534	$ (1,397,962)	1,296,536	1,406,720	(699)	1,305,129
Balance (in shares) at Mar. 31, 2018	53,398	(28,771)
Balance at Dec. 31, 2018	$ 535	$ (1,461,002)	1,326,645	1,419,449	(324)	1,285,303
Balance (in shares) at Dec. 31, 2018	53,536	(29,601)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense			9,607			9,607
Exercise of stock options	$ 1		2,044			2,045
Exercise of stock options (in shares)	41
Issuance of equity	$ 1		(447)			(446)
Issuance of equity (in shares)	118
Repurchase of stock		$ (3,725)				(3,725)
Repurchase of stock (in shares)		(61)
Net income				431		431
Other comprehensive income (loss)-other					320	320
Adoption of new accounting standards				(145)		(145)
Balance at Mar. 31, 2019	$ 537	$ (1,464,727)	$ 1,337,849	$ 1,419,735	$ (4)	$ 1,293,390
Balance (in shares) at Mar. 31, 2019	53,695	(29,662)