Retirement Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Retirement Plans	Retirement Plans: We have trusteed, noncontributory retirement plans for most of our full-time employees. Contributions are discretionary and amounts accrued were approximately $4.7 million and $4.2 million for the years ended December 31, 2019 and 2018, respectively. For the year ended December 31, 2020, we did not make any discretionary contributions due to the effects of the COVID-19 pandemic on our financial performance. Additionally, we have a trusteed, contributory retirement plan for most of our full-time employees. This plan permits employees to contribute specified percentages of their salary, matched up to a limit. Matching contributions, net of forfeitures, approximated $3.8 million, $3.1 million and $2.6 million for the years ended December 31, 2020, 2019 and 2018, respectively.In addition, approximately 250 employees are covered by union-sponsored, multi-employer pension plans for which approximately $2.0 million, $2.0 million and $1.8 million were contributed for the years ended December 31, 2020, 2019 and 2018, respectively. We have no plans to withdraw from any of the multi-employer plans.