| Schedule of Stockholders Equity | The following tables present changes in our equity for the nine months ended September 30, 2023 and 2022 (in thousands, except shares and per share amounts): 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Common Stock |  | Treasury Stock |  | Additional Paid-in Capital |  | Accum. Other
 Comp.
 Income (Loss)
 |  | Retained Earnings |  | Total Equity
 |  
|  | Shares |  | Amount |  | Shares |  | Amount |  |  |  |  |  
| For the nine months ended September 30, 2023: |  |  |  |  |  |  |  |  |  |  |  |  |  
| Balances as of December 31, 2022 | 7,695,679 |  |  | $ | 78 |  |  | 60,477 |  |  | $ | (104,139) |  |  | $ | 8,293 |  |  | $ | 2,516 |  |  | $ | 866,139 |  |  | $ | 772,887 |  |  
| Net income | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 86,568 |  |  | 86,568 |  |  
| Dividends paid — $3.25 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (25,061) |  |  | (25,061) |  |  
| Share-based compensation, net of forfeitures | 1,756 |  |  | — |  |  | (1,756) |  |  | 3,033 |  |  | (560) |  |  | — |  |  | (103) |  |  | 2,370 |  |  
| Repurchases of common stock, including excise taxes of $67 | (3,627) |  |  | — |  |  | 3,627 |  |  | (6,749) |  |  | — |  |  | — |  |  | — |  |  | (6,749) |  |  
| Shares exchanged for tax withholdings | (488) |  |  | — |  |  | 488 |  |  | (939) |  |  | — |  |  | — |  |  | — |  |  | (939) |  |  
| Periodic pension costs, net of income taxes of $6 | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (25) |  |  | — |  |  | (25) |  |  
| Balances as of March 31, 2023 | 7,693,320 |  |  | 78 |  |  | 62,836 |  |  | (108,794) |  |  | 7,733 |  |  | 2,491 |  |  | 927,543 |  |  | 829,051 |  |  
| Net income | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 100,393 |  |  | 100,393 |  |  
| Dividends paid — $3.25 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (24,966) |  |  | (24,966) |  |  
| Share-based compensation, net of forfeitures | — |  |  | — |  |  | — |  |  | — |  |  | 2,849 |  |  | — |  |  | (43) |  |  | 2,806 |  |  
| Repurchases of common stock, including excise taxes of $165 | (14,175) |  |  | — |  |  | 14,175 |  |  | (19,708) |  |  | — |  |  | — |  |  | — |  |  | (19,708) |  |  
| Periodic pension costs, net of income taxes of $8 | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (26) |  |  | — |  |  | (26) |  |  
| Balances as of June 30, 2023 | 7,679,145 |  |  | 78 |  |  | 77,011 |  |  | (128,502) |  |  | 10,582 |  |  | 2,465 |  |  | 1,002,927 |  |  | 887,550 |  |  
| Net income | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 105,574 |  |  | 105,574 |  |  
| Dividends paid — $3.25 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (24,952) |  |  | (24,952) |  |  
| Share-based compensation, net of forfeitures | 594 |  |  | — |  |  | (594) |  |  | 990 |  |  | 1,800 |  |  | — |  |  | (38) |  |  | 2,752 |  |  
| Repurchases of common stock, including excise taxes of $50 | (3,564) |  |  | — |  |  | 3,564 |  |  | (5,995) |  |  | — |  |  | — |  |  | — |  |  | (5,995) |  |  
| Shares exchanged for tax withholdings | (181) |  |  | — |  |  | 181 |  |  | (345) |  |  | — |  |  | — |  |  | — |  |  | (345) |  |  
| Periodic pension costs, net of income taxes of $7 | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (26) |  |  | — |  |  | (26) |  |  
| Balances as of September 30, 2023 | 7,675,994 |  |  | $ | 78 |  |  | 80,162 |  |  | $ | (133,852) |  |  | $ | 12,382 |  |  | $ | 2,439 |  |  | $ | 1,083,511 |  |  | $ | 964,558 |  | 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Common Stock |  | Treasury Stock |  | Additional Paid-in Capital |  | Accum. Other
 Comp.
 Income (Loss)
 |  | Retained Earnings |  | Total Equity
 |  
|  | Shares |  | Amount |  | Shares |  | Amount |  |  |  |  |  
| For the nine months ended September 30, 2022: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Balances as of December 31, 2021 | 7,744,695 |  |  | $ | 78 |  |  | 11,461 |  |  | $ | (15,417) |  |  | $ | 28 |  |  | $ | (1,007) |  |  | $ | 668,029 |  |  | $ | 651,711 |  |  
| Net income | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 97,900 |  |  | 97,900 |  |  
| Dividends paid — $3.00 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (23,224) |  |  | (23,224) |  |  
| Share-based compensation, net of forfeitures | 595 |  |  | — |  |  | (595) |  |  | 800 |  |  | 1,477 |  |  | — |  |  | (796) |  |  | 1,481 |  |  
| Periodic pension costs, net of income taxes of $2 | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 8 |  |  | — |  |  | 8 |  |  
| Balances as of March 31, 2022 | 7,745,290 |  |  | 78 |  |  | 10,866 |  |  | (14,617) |  |  | 1,505 |  |  | (999) |  |  | 741,909 |  |  | 727,876 |  |  
| Net income | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 118,894 |  |  | 118,894 |  |  
| Dividends paid — $3.00 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (23,188) |  |  | (23,188) |  |  
| Special dividends paid — $20.00 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (154,586) |  |  | (154,586) |  |  
| Share-based compensation, net of forfeitures | 104 |  |  | — |  |  | (104) |  |  | 140 |  |  | 1,851 |  |  | — |  |  | (180) |  |  | 1,811 |  |  
| Repurchases of common stock | (17,478) |  |  | — |  |  | 17,478 |  |  | (25,534) |  |  | — |  |  | — |  |  | — |  |  | (25,534) |  |  
| Periodic pension costs, net of income taxes of $2 | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 8 |  |  | — |  |  | 8 |  |  
| Balances as of June 30, 2022 | 7,727,916 |  |  | 78 |  |  | 28,240 |  |  | (40,011) |  |  | 3,356 |  |  | (991) |  |  | 682,849 |  |  | 645,281 |  |  
| Net income | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 129,837 |  |  | 129,837 |  |  
| Dividends paid — $3.00 per share of common stock | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (23,132) |  |  | (23,132) |  |  
| Share-based compensation, net of forfeitures | — |  |  | — |  |  | — |  |  | — |  |  | 2,121 |  |  | — |  |  | (30) |  |  | 2,091 |  |  
| Repurchases of common stock | (19,071) |  |  | — |  |  | 19,071 |  |  | (32,915) |  |  | — |  |  | — |  |  | — |  |  | (32,915) |  |  
| Periodic pension costs, net of income taxes of $3 | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 8 |  |  | — |  |  | 8 |  |  
| Balances as of September 30, 2022 | 7,708,845 |  |  | $ | 78 |  |  | 47,311 |  |  | $ | (72,926) |  |  | $ | 5,477 |  |  | $ | (983) |  |  | $ | 789,524 |  |  | $ | 721,170 |  |  |