Significant Accounting Policies - Income Taxes (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Dividends Payable [Line Items]
SUMMIT Operator tax expense	$ 9,201	$ 2,647	$ 1,000
Federal, state and local tax provision	$ 8,200	$ 3,700	$ 2,800
Dividends per share paid (in dollars per share)	$ 3.25	$ 6.17	$ 8.09
Ordinary Income Dividend
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)	0.00	2.56	0.50
Capital Gains Dividend
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)	$ 3.25	$ 1.17	$ 5.92