Income Taxes (Federal Statutory Income Tax Rate to Income Before Income Taxes) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income (loss) from operations before income taxes	$ (398,987,000)	$ 100,721,000	$ (10,294,000)
Partnership income not subject to federal income tax	398,729,000	(99,832,000)	10,824,000
Income (loss) subject to federal income taxes	(258,000)	889,000	530,000
Tax expense (benefit) at federal statutory rate	(54,000)	187,000	111,000
State income taxes, net of federal tax	1,213,000	729,000	1,285,000
Return to provision, federal and state	(383,000)	(219,000)	(128,000)
Other	117,000	(42,000)	230,000
Valuation allowance	434,000	0	0
Income tax expense	$ 1,327,000	$ 655,000	$ 1,498,000
Effective tax rate on income (loss) from operations before income taxes	(0.30%)	0.70%	(14.60%)
Liability for uncertain tax positions	$ 0	$ 0	$ 0