CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Common Stock In Treasury	Additional Paid in Capital	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Cumulative Effect, Period of Adoption, Adjustment	Total
Balance at Dec. 31, 2019	$ 543	$ (1,464,727)	$ 1,386,616		$ 1,475,207	$ 144		$ 1,397,783
Balance (in shares) at Dec. 31, 2019	54,285,000	(29,662,000)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense			6,057					6,057
Exercise of stock options	$ 2		11,261					11,263
Exercise of stock options (in shares)	216,000
Issuance of equity	$ 1		(1,137)					(1,136)
Issuance of equity (in shares)	130,000
Net income					18,250			18,250
Other comprehensive income (loss)-other						(201)		(201)
Balance at Mar. 31, 2020	$ 546	$ (1,464,727)	1,402,797	$ (413)	1,493,044	(57)	$ (413)	1,431,603
Balance (in shares) at Mar. 31, 2020	54,631,000	(29,662,000)
Balance at Dec. 31, 2020	$ 555	$ (1,464,727)	1,477,219		1,857,130	(205)		$ 1,869,972
Balance (in shares) at Dec. 31, 2020	55,549,000	(29,662,000)						25,887,000
Increase (Decrease) in Stockholders' Equity
Stock compensation expense			7,057					$ 7,057
Exercise of stock options	$ 2		7,465					$ 7,467
Exercise of stock options (in shares)	110,000							109,381
Issuance of equity	$ 1		(2,766)					$ (2,765)
Issuance of equity (in shares)	130,000
Net income					27,827			27,827
Other comprehensive income (loss)-other						10		10
Balance at Mar. 31, 2021	$ 558	$ (1,464,727)	$ 1,488,975		$ 1,884,957	$ (195)		$ 1,909,568
Balance (in shares) at Mar. 31, 2021	55,789,000	(29,662,000)						26,127,000