Significant Accounting Policies - Income Taxes (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Dividends Payable [Line Items]
SUMMIT Operator tax expense	$ 730	$ 9,201	$ 2,647
Federal, state and local tax provision	$ 700	$ 9,200	$ 2,600
Dividends per share paid (in dollars per share)	$ 3.16	$ 3.25	$ 6.17
Internal Revenue Service (IRS)
Dividends Payable [Line Items]
SUMMIT Operator tax expense	$ 4,900	$ 8,200	$ 3,700
O 2024 A Dividends
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)	$ 0.23
O 2023 A Dividends
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)		$ 0.00
O 2022 A Dividends
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)			$ 2.56
Capital Gains 2024 Dividend
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)	$ 2.93
Capital Gains 2023 Dividend
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)		$ 3.25
Capital Gains 2022 Dividend
Dividends Payable [Line Items]
Dividends per share paid (in dollars per share)			$ 1.17