Equity Compensation and Employee Benefit Plans (Contributions and Administrative Expenses Under 401(k) Retirement Savings Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan contributions and administrative expenses	$ 4,748	$ 4,414	$ 2,615