Debt - Schedule of Mortgage Notes Payable (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt
Outstanding principal balance	$ 875,286	$ 917,655
Unamortized deferred financing costs	(12,694)	(14,125)
Debt, net	$ 996,393
ABS Program
Debt
Weighted average contractual interest rate (in percentage)	5.28%
Outstanding principal balance	$ 134,749	134,898
ABS Program \| New Mountain Net Lease Partners II, L.P
Debt
Outstanding principal balance	357,978
ABS Program, Class A notes
Debt
Amount of debt instrument	$ 338,300
Weighted average contractual interest rate (in percentage)	5.14%
Outstanding principal balance	$ 92,391	92,493
ABS Program, Class A notes \| New Mountain Net Lease Partners II, L.P
Debt
Amount of debt instrument	245,448
ABS Program, Class B notes
Debt
Amount of debt instrument	$ 98,700
Weighted average contractual interest rate (in percentage)	5.33%
Outstanding principal balance	$ 26,955	26,985
ABS Program, Class B notes \| New Mountain Net Lease Partners II, L.P
Debt
Amount of debt instrument	71,610
ABS Program, Class C notes
Debt
Amount of debt instrument	$ 56,400
Weighted average contractual interest rate (in percentage)	6.07%
Outstanding principal balance	$ 15,403	15,420
ABS Program, Class C notes \| New Mountain Net Lease Partners II, L.P
Debt
Amount of debt instrument	$ 40,920
Mortgages At 3.98 Interest
Debt
Weighted average contractual interest rate (in percentage)	3.98%
Outstanding principal balance	$ 740,537	782,757
Mortgage notes
Debt
Unamortized deferred financing costs	(12,032)	(13,303)
Debt, net	$ 863,254	$ 904,352