Consolidated Statements of Stockholders' Equity Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2019	$ 21,640,000	$ 206,000	$ 5,817,000	$ (5,000)	$ 15,649,000	$ (27,000)
Net Income (Loss)	(900,000)	0	0	0	(900,000)	0
Dividends, Common Stock	(437,000)	0	0	0	(437,000)	0
Other Comprehensive Loss	0	0	0	0	0	0
Change in Treasury Stock - Stock Compensation Plans, Net	4,000	0	(7,000)	0	0	11,000
Restricted Stock and Restricted Stock Units, Net	0	0	(4,000)	0	0	4,000
Stock-Based Compensation Expenses	80,000	0	80,000	0	0	0
Treasury Stock Issued as Compensation	1,000	0	0	0	0	1,000
Balance at Jun. 30, 2020	20,388,000	206,000	5,886,000	(5,000)	14,312,000	(11,000)
Balance at Mar. 31, 2020	21,471,000	206,000	5,853,000	(3,000)	15,440,000	(25,000)
Net Income (Loss)	(910,000)	0	0	0	(910,000)	0
Dividends, Common Stock	(218,000)	0	0	0	(218,000)	0
Other Comprehensive Loss	(2,000)	0	0	(2,000)	0	0
Change in Treasury Stock - Stock Compensation Plans, Net	7,000	0	(7,000)	0	0	14,000
Restricted Stock and Restricted Stock Units, Net	0	0	0	0	0	0
Stock-Based Compensation Expenses	40,000	0	40,000	0	0	0
Treasury Stock Issued as Compensation	0	0	0	0	0	0
Balance at Jun. 30, 2020	20,388,000	206,000	5,886,000	(5,000)	14,312,000	(11,000)
Balance at Dec. 31, 2020	20,302,000	206,000	5,945,000	(12,000)	14,170,000	(7,000)
Net Income (Loss)	1,584,000	0	0	0	1,584,000	0
Dividends, Common Stock	(1,065,000)	0	0	0	(1,065,000)	0
Other Comprehensive Loss	(3,000)	0	0	(3,000)	0	0
Common Stock Issued Under Stock Plans	9,000	0	9,000	0	0	0
Change in Treasury Stock - Stock Compensation Plans, Net	(12,000)	0	(2,000)	0	0	(10,000)
Restricted Stock and Restricted Stock Units, Net	0	0	(1,000)	0	0	1,000
Stock-Based Compensation Expenses	66,000	0	66,000	0	0	0
Treasury Stock Issued as Compensation	0	0	0	0	0	0
Balance at Jun. 30, 2021	20,881,000	206,000	6,017,000	(15,000)	14,689,000	(16,000)
Balance at Mar. 31, 2021	20,762,000	206,000	5,979,000	(14,000)	14,606,000	(15,000)
Net Income (Loss)	907,000	0	0	0	907,000	0
Dividends, Common Stock	(824,000)	0	0	0	(824,000)	0
Other Comprehensive Loss	(1,000)	0	0	(1,000)	0	0
Common Stock Issued Under Stock Plans	9,000	0	9,000	0	0	0
Change in Treasury Stock - Stock Compensation Plans, Net	(3,000)	0	(2,000)	0	0	(1,000)
Restricted Stock and Restricted Stock Units, Net	0	0	0	0	0	0
Stock-Based Compensation Expenses	31,000	0	31,000	0	0	0
Treasury Stock Issued as Compensation	0	0	0	0	0	0
Balance at Jun. 30, 2021	$ 20,881,000	$ 206,000	$ 6,017,000	$ (15,000)	$ 14,689,000	$ (16,000)